diff --git a/pom.xml b/pom.xml
index 2bb89de..6de0e12 100644
--- a/pom.xml
+++ b/pom.xml
@@ -12,6 +12,7 @@
   <properties>
     <maven.compiler.source>21</maven.compiler.source>
     <maven.compiler.target>21</maven.compiler.target>
+    <maven.compiler.release>21</maven.compiler.release>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>
 
@@ -26,6 +27,11 @@
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-websocket</artifactId>
+    </dependency>
+
     <dependency>
       <groupId>org.projectlombok</groupId>
       <artifactId>lombok</artifactId>
diff --git a/src/main/angular/angular.json b/src/main/angular/angular.json
index 5f9d590..1a8aac4 100644
--- a/src/main/angular/angular.json
+++ b/src/main/angular/angular.json
@@ -72,6 +72,12 @@
                   "maximumError": "4kB"
                 }
               ],
+              "fileReplacements": [
+                {
+                  "replace": "src/environments/environment.ts",
+                  "with": "src/environments/environment.prod.ts"
+                }
+              ],
               "outputHashing": "all"
             },
             "development": {
diff --git a/src/main/angular/package-lock.json b/src/main/angular/package-lock.json
index 487ac50..d568a21 100644
--- a/src/main/angular/package-lock.json
+++ b/src/main/angular/package-lock.json
@@ -16,6 +16,8 @@
         "@angular/platform-browser": "^18.2.0",
         "@angular/platform-browser-dynamic": "^18.2.0",
         "@angular/router": "^18.2.0",
+        "@stomp/ng2-stompjs": "^8.0.0",
+        "ngx-cookie-service": "^18.0.0",
         "rxjs": "~7.8.0",
         "tslib": "^2.3.0",
         "zone.js": "~0.14.10"
@@ -4283,6 +4285,39 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@stomp/ng2-stompjs": {
+      "version": "8.0.0",
+      "resolved": "https://registry.npmjs.org/@stomp/ng2-stompjs/-/ng2-stompjs-8.0.0.tgz",
+      "integrity": "sha512-1TTwdK7aUaRLfewG2FOqd3ZeIyIchKwOBzJytvUckjrBbpdeAXLXY0mCBFczoY16fSsxiAnZfJffFicStD+Dug==",
+      "deprecated": "Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@stomp/rx-stomp": "^1.0.0 >=1.0.1",
+        "tslib": "^1.9.0"
+      }
+    },
+    "node_modules/@stomp/ng2-stompjs/node_modules/tslib": {
+      "version": "1.14.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.14.1.tgz",
+      "integrity": "sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==",
+      "license": "0BSD"
+    },
+    "node_modules/@stomp/rx-stomp": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/@stomp/rx-stomp/-/rx-stomp-1.2.0.tgz",
+      "integrity": "sha512-QLzPe3q0EwLB+cVWdUFEO4z5tyR+kPnXJANKN2UvB7Spz/oViHF959cydmXdQWaK7NHp86VO54TgFfXbHVnSLg==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@stomp/stompjs": "^6.0.0 >=6.1.1",
+        "angular2-uuid": "^1.1.1"
+      }
+    },
+    "node_modules/@stomp/stompjs": {
+      "version": "6.1.2",
+      "resolved": "https://registry.npmjs.org/@stomp/stompjs/-/stompjs-6.1.2.tgz",
+      "integrity": "sha512-FHDTrIFM5Ospi4L3Xhj6v2+NzCVAeNDcBe95YjUWhWiRMrBF6uN3I7AUOlRgT6jU/2WQvvYK8ZaIxFfxFp+uHQ==",
+      "license": "Apache-2.0"
+    },
     "node_modules/@tufjs/canonical-json": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/@tufjs/canonical-json/-/canonical-json-2.0.0.tgz",
@@ -4943,6 +4978,12 @@
         "ajv": "^8.8.2"
       }
     },
+    "node_modules/angular2-uuid": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/angular2-uuid/-/angular2-uuid-1.1.1.tgz",
+      "integrity": "sha512-6AXPyii9q8KBFGagybLNVmdGJLPcVZAhmv3odNGSJIA18LuJ3xOe6uN9GvjlQsGfdmYeuxlsGnFEUu7gPhkc+g==",
+      "license": "MIT"
+    },
     "node_modules/ansi-colors": {
       "version": "4.1.3",
       "resolved": "https://registry.npmjs.org/ansi-colors/-/ansi-colors-4.1.3.tgz",
@@ -10100,6 +10141,19 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/ngx-cookie-service": {
+      "version": "18.0.0",
+      "resolved": "https://registry.npmjs.org/ngx-cookie-service/-/ngx-cookie-service-18.0.0.tgz",
+      "integrity": "sha512-hkkUckzZTXXWtFgvVkT2hg6mwYMLXioXDZWBsVCOy9gYkADjsj0N5VViO7eo2izQ0VcMPd/Etog1trf/T4oZMQ==",
+      "license": "MIT",
+      "dependencies": {
+        "tslib": "^2.6.2"
+      },
+      "peerDependencies": {
+        "@angular/common": "^18.0.0-rc.0",
+        "@angular/core": "^18.0.0-rc.0"
+      }
+    },
     "node_modules/nice-napi": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/nice-napi/-/nice-napi-1.0.2.tgz",
diff --git a/src/main/angular/package.json b/src/main/angular/package.json
index 6f11947..f2fb28f 100644
--- a/src/main/angular/package.json
+++ b/src/main/angular/package.json
@@ -20,7 +20,9 @@
     "@angular/router": "^18.2.0",
     "rxjs": "~7.8.0",
     "tslib": "^2.3.0",
-    "zone.js": "~0.14.10"
+    "zone.js": "~0.14.10",
+    "@stomp/ng2-stompjs": "^8.0.0",
+    "ngx-cookie-service": "^18.0.0"
   },
   "devDependencies": {
     "@angular-devkit/build-angular": "^18.2.3",
diff --git a/src/main/angular/src/app/api/Session/AbstractSession.ts b/src/main/angular/src/app/api/Session/AbstractSession.ts
new file mode 100644
index 0000000..142b8e2
--- /dev/null
+++ b/src/main/angular/src/app/api/Session/AbstractSession.ts
@@ -0,0 +1,20 @@
+import {UserPublic} from "../User/UserPublic";
+
+export abstract class AbstractSession {
+
+  protected constructor(
+    readonly type: string,
+    readonly typeDisplayName: string,
+    readonly uuid: string,
+    readonly owner: UserPublic,
+    readonly created: Date,
+    readonly title: string,
+    readonly password: string,
+    readonly users: UserPublic[],
+    readonly initial: boolean,
+  ) {
+    // -
+  }
+
+}
+
diff --git a/src/main/angular/src/app/api/Session/AbstractSessionService.ts b/src/main/angular/src/app/api/Session/AbstractSessionService.ts
new file mode 100644
index 0000000..d51e116
--- /dev/null
+++ b/src/main/angular/src/app/api/Session/AbstractSessionService.ts
@@ -0,0 +1,70 @@
+import {ApiService} from "../common/api.service";
+import {FromJson, Next} from "../common/types";
+import {AbstractSession} from "./AbstractSession";
+import {Router} from "@angular/router";
+import {UserService} from "../User/user.service";
+import {validateBoolean} from "../common/validators";
+
+export abstract class AbstractSessionService<SESSION extends AbstractSession> {
+
+  protected constructor(
+    protected readonly api: ApiService,
+    protected readonly router: Router,
+    protected readonly userService: UserService,
+    readonly apiPath: any[],
+    readonly routerPath: any[],
+    readonly fromJson: FromJson<SESSION>,
+  ) {
+    // -
+  }
+
+  canAccess(uuid: string, next: Next<boolean>): void {
+    this.api.postSingle([...this.apiPath, 'canAccess'], uuid, validateBoolean, next);
+  }
+
+  get(uuid: string, next: Next<SESSION>): void {
+    this.api.postSingle([...this.apiPath, 'get'], uuid, this.fromJson, next);
+  }
+
+  create(next: Next<SESSION>): void {
+    this.api.getSingle([...this.apiPath, 'create'], this.fromJson, session => {
+      next(session);
+      this.userService.refresh();
+    });
+  }
+
+  changeTitle(session: SESSION, title: string, next?: Next<SESSION>) {
+    const data = {
+      uuid: session.uuid,
+      title: title,
+    };
+    this.api.postSingle([...this.apiPath, 'changeTitle'], data, this.fromJson, next);
+  }
+
+  changePassword(session: SESSION, password: string, next?: Next<SESSION>) {
+    const data = {
+      uuid: session.uuid,
+      password: password,
+    };
+    this.api.postSingle([...this.apiPath, 'changePassword'], data, this.fromJson, next);
+  }
+
+  join(uuid: string, password: string, next: Next<SESSION>): void {
+    const data = {
+      uuid: uuid,
+      password: password,
+    };
+    this.api.postSingle([...this.apiPath, 'join'], data, this.fromJson, next);
+  }
+
+  leave(session: SESSION, next: Next<void>): void {
+    this.api.postNone([...this.apiPath, 'leave'], session, next);
+  }
+
+  goto(session: SESSION) {
+    const url = '/' + this.routerPath.join('/');
+    this.router.navigate([url, {uuid: session.uuid}]);
+  }
+
+}
+
diff --git a/src/main/angular/src/app/api/Session/sessionFromJsonOrNull.ts b/src/main/angular/src/app/api/Session/sessionFromJsonOrNull.ts
new file mode 100644
index 0000000..96960be
--- /dev/null
+++ b/src/main/angular/src/app/api/Session/sessionFromJsonOrNull.ts
@@ -0,0 +1,14 @@
+import {AbstractSession} from "./AbstractSession";
+import {validateString} from "../common/validators";
+import {NumbersSession} from "../tools/Numbers/Session/NumbersSession";
+
+export function sessionFromJsonOrNull(json: any): AbstractSession | null {
+  const type = validateString(json['type']);
+  switch (type) {
+    case 'Numbers':
+      return NumbersSession.fromJson(json);
+    default:
+      console.error("Not implemented: AbstractSession.type=" + type);
+      return null;
+  }
+}
diff --git a/src/main/angular/src/app/api/User/UserCommon.ts b/src/main/angular/src/app/api/User/UserCommon.ts
new file mode 100644
index 0000000..c21bf41
--- /dev/null
+++ b/src/main/angular/src/app/api/User/UserCommon.ts
@@ -0,0 +1,24 @@
+import {validateListIgnoreNullItems, validateString} from "../common/validators";
+import {AbstractSession} from "../Session/AbstractSession";
+import {sessionFromJsonOrNull} from "../Session/sessionFromJsonOrNull";
+import {UserPublic} from "./UserPublic";
+
+export class UserCommon extends UserPublic {
+
+  constructor(
+    publicUuid: string,
+    name: string,
+    readonly commonSessions: AbstractSession[],
+  ) {
+    super(publicUuid, name);
+  }
+
+  static override fromJson(json: any): UserCommon {
+    return new UserCommon(
+      validateString(json['publicUuid']),
+      validateString(json['name']),
+      validateListIgnoreNullItems(json['commonSessions'], sessionFromJsonOrNull),
+    );
+  }
+
+}
diff --git a/src/main/angular/src/app/api/User/UserPrivate.ts b/src/main/angular/src/app/api/User/UserPrivate.ts
new file mode 100644
index 0000000..4b51507
--- /dev/null
+++ b/src/main/angular/src/app/api/User/UserPrivate.ts
@@ -0,0 +1,35 @@
+import {validateDate, validateListIgnoreNullItems, validateString} from "../common/validators";
+import {AbstractSession} from "../Session/AbstractSession";
+
+import {sessionFromJsonOrNull} from "../Session/sessionFromJsonOrNull";
+
+export class UserPrivate {
+
+  constructor(
+    readonly privateUuid: string,
+    readonly publicUuid: string,
+    readonly created: Date,
+    readonly sessions: AbstractSession[],
+    readonly name: string,
+  ) {
+    // -
+  }
+
+  static fromJson(json: any): UserPrivate {
+    return new UserPrivate(
+      validateString(json['privateUuid']),
+      validateString(json['publicUuid']),
+      validateDate(json['created']),
+      validateListIgnoreNullItems(json['sessions'], sessionFromJsonOrNull),
+      validateString(json['name']),
+    );
+  }
+
+  static fromJsonOrNull(json: any): UserPrivate | null {
+    if (json === null || json === undefined) {
+      return null;
+    }
+    return UserPrivate.fromJson(json);
+  }
+
+}
diff --git a/src/main/angular/src/app/api/User/UserPublic.ts b/src/main/angular/src/app/api/User/UserPublic.ts
new file mode 100644
index 0000000..d186e3e
--- /dev/null
+++ b/src/main/angular/src/app/api/User/UserPublic.ts
@@ -0,0 +1,19 @@
+import {validateString} from "../common/validators";
+
+export class UserPublic {
+
+  constructor(
+    readonly publicUuid: string,
+    readonly name: string,
+  ) {
+    // -
+  }
+
+  static fromJson(json: any): UserPublic {
+    return new UserPublic(
+      validateString(json['publicUuid']),
+      validateString(json['name']),
+    );
+  }
+
+}
diff --git a/src/main/angular/src/app/api/User/user.service.ts b/src/main/angular/src/app/api/User/user.service.ts
new file mode 100644
index 0000000..26cc05f
--- /dev/null
+++ b/src/main/angular/src/app/api/User/user.service.ts
@@ -0,0 +1,60 @@
+import {Injectable} from '@angular/core';
+import {ApiService} from "../common/api.service";
+import {UserPrivate} from "./UserPrivate";
+import {Next} from "../common/types";
+import {UserCommon} from "./UserCommon";
+import {UserPublic} from "./UserPublic";
+import {Router} from "@angular/router";
+import {BehaviorSubject, Subscription} from "rxjs";
+import {AbstractSession} from "../Session/AbstractSession";
+
+@Injectable({
+  providedIn: 'root'
+})
+export class UserService {
+
+  private readonly subject: BehaviorSubject<UserPrivate | null> = new BehaviorSubject<UserPrivate | null>(null);
+
+  get user(): UserPrivate | null {
+    return this.subject.value;
+  }
+
+  constructor(
+    protected readonly router: Router,
+    protected readonly api: ApiService,
+  ) {
+    this.refresh();
+  }
+
+  getCommonByUuid(uuid: string, next: Next<UserCommon>): void {
+    this.api.postSingle(['User', 'getCommonByUuid'], uuid, UserCommon.fromJson, next);
+  }
+
+  delete(next?: Next<void>) {
+    this.api.getNone(['User', 'delete'], _ => {
+      this.refresh();
+      next && next();
+    });
+  }
+
+  changeName(name: string, next?: Next<UserPrivate>) {
+    this.api.postSingle(['User', 'changeName'], name, UserPrivate.fromJson, next);
+  }
+
+  goto(user: UserPublic) {
+    this.router.navigate(['/User', {uuid: user.publicUuid}]);
+  }
+
+  refresh() {
+    this.api.getSingle(['User', 'whoAmI'], UserPrivate.fromJsonOrNull, user => this.subject.next(user));
+  }
+
+  subscribe(next: Next<UserPrivate | null>): Subscription {
+    return this.subject.subscribe(next);
+  }
+
+  owns(session: AbstractSession): boolean {
+    return this.user?.publicUuid === session.owner.publicUuid;
+  }
+
+}
diff --git a/src/main/angular/src/app/api/common/CrudDirection.ts b/src/main/angular/src/app/api/common/CrudDirection.ts
new file mode 100644
index 0000000..712430a
--- /dev/null
+++ b/src/main/angular/src/app/api/common/CrudDirection.ts
@@ -0,0 +1,4 @@
+export enum CrudDirection {
+  ASC = 'ASC',
+  DESC = 'DESC',
+}
diff --git a/src/main/angular/src/app/api/common/Order.ts b/src/main/angular/src/app/api/common/Order.ts
new file mode 100644
index 0000000..452cc3a
--- /dev/null
+++ b/src/main/angular/src/app/api/common/Order.ts
@@ -0,0 +1,13 @@
+import {CrudDirection} from "./CrudDirection";
+
+export class Order<T> {
+
+  constructor(
+    readonly property: string,
+    readonly compare: (a: T, b: T) => number,
+    public direction: CrudDirection,
+  ) {
+    // -
+  }
+
+}
diff --git a/src/main/angular/src/app/api/common/Page.ts b/src/main/angular/src/app/api/common/Page.ts
new file mode 100644
index 0000000..a90508f
--- /dev/null
+++ b/src/main/angular/src/app/api/common/Page.ts
@@ -0,0 +1,28 @@
+import {validateList, validateNumber} from "./validators";
+import {FromJson} from "./types";
+
+export class Page<T> {
+
+  static readonly EMPTY: Page<any> = new Page(0, 0, 0, 0, []);
+
+  constructor(
+    readonly size: number,
+    readonly number: number,
+    readonly totalPages: number,
+    readonly totalElements: number,
+    readonly content: T[],
+  ) {
+    // -
+  }
+
+  static fromJson<T>(fromJson: FromJson<T>): FromJson<Page<T>> {
+    return (json: any) => new Page<T>(
+      validateNumber(json.page.size),
+      validateNumber(json.page.number),
+      validateNumber(json.page.totalPages),
+      validateNumber(json.page.totalElements),
+      validateList(json.content, fromJson),
+    );
+  }
+
+}
diff --git a/src/main/angular/src/app/api/common/Sort.ts b/src/main/angular/src/app/api/common/Sort.ts
new file mode 100644
index 0000000..aeecbe1
--- /dev/null
+++ b/src/main/angular/src/app/api/common/Sort.ts
@@ -0,0 +1,65 @@
+import {CrudDirection} from "./CrudDirection";
+
+import {Order} from "./Order";
+
+export class Sort<T> {
+
+  private list: Order<T>[] = [];
+
+  toggle(key: string, compare: (a: T, b: T) => number) {
+    const index: number = this.indexOf(key);
+    if (index >= 0) {
+      const existing: Order<T> = this.list[index];
+      if (existing.direction === CrudDirection.ASC) {
+        existing.direction = CrudDirection.DESC;
+      } else {
+        this.list.splice(index, 1);
+      }
+    } else {
+      this.list.push(new Order(key, compare, CrudDirection.ASC));
+    }
+  }
+
+  compare(a: T, b: T): number {
+    for (const order of this.list) {
+      const result = order.compare(a, b);
+      if (result != 0) {
+        return order.direction === CrudDirection.DESC ? -result : result;
+      }
+    }
+    return 0;
+  }
+
+  isEmpty(): boolean {
+    return this.list.length === 0;
+  }
+
+  indexOf(key: string): number {
+    return this.list.findIndex(o => o.property === key);
+  }
+
+  isActive(key: string): boolean {
+    return this.indexOf(key) >= 0;
+  }
+
+  isAscending(key: string): boolean {
+    return this.isDirection(key, CrudDirection.ASC);
+  }
+
+  isDescending(key: string): boolean {
+    return this.isDirection(key, CrudDirection.DESC);
+  }
+
+  isDirection(key: string, direction: CrudDirection): boolean {
+    const index: number = this.indexOf(key);
+    if (index < 0) {
+      return false;
+    }
+    return this.list[index].direction === direction;
+  }
+
+  clear(): void {
+    this.list = [];
+  }
+
+}
diff --git a/src/main/angular/src/app/api/common/api.service.ts b/src/main/angular/src/app/api/common/api.service.ts
new file mode 100644
index 0000000..92e8cb7
--- /dev/null
+++ b/src/main/angular/src/app/api/common/api.service.ts
@@ -0,0 +1,75 @@
+import {Injectable} from '@angular/core';
+import {HttpClient} from "@angular/common/http";
+import {map, Subscription} from "rxjs";
+import {FromJson, getApiUrl, Next} from "./types";
+import {Page} from "./Page";
+import {StompService} from "@stomp/ng2-stompjs";
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ApiService {
+
+  private _websocketError: boolean = false;
+
+  get websocketError(): boolean {
+    return this._websocketError;
+  }
+
+  constructor(
+    private readonly http: HttpClient,
+    private readonly stompService: StompService,
+  ) {
+    stompService.connected$.subscribe(() => this._websocketError = false);
+    stompService.webSocketErrors$.subscribe(() => this._websocketError = true);
+  }
+
+  connected(next: Next<void>): Subscription {
+    return this.stompService.connected$.subscribe(_ => next());
+  }
+
+  subscribe<T>(topic: any[], fromJson: FromJson<T>, next: Next<T>): Subscription {
+    console.info("WEBSOCKET SUBSCRIBE", topic)
+    return this.stompService
+      .subscribe(topic.join("/"))
+      .pipe(
+        map(message => message.body),
+        map(b => JSON.parse(b)),
+        map(j => fromJson(j)),
+      )
+      .subscribe(next);
+  }
+
+  getNone<T>(path: any[], next?: Next<void>): Subscription {
+    return this.http.get<void>(getApiUrl('http', path), {withCredentials: true}).subscribe(next);
+  }
+
+  getString(path: any[], next: Next<string>): Subscription {
+    return this.http.get(getApiUrl('http', path), {responseType: "text", withCredentials: true}).subscribe(next);
+  }
+
+  getSingle<T>(path: any[], fromJson: FromJson<T>, next?: Next<T>): Subscription {
+    return this.http.get<any>(getApiUrl('http', path), {withCredentials: true}).pipe(map(fromJson)).subscribe(next);
+  }
+
+  getList<T>(path: any[], fromJson: FromJson<T>, next: Next<T[]> | undefined = undefined): Subscription {
+    return this.http.get<any[]>(getApiUrl('http', path), {withCredentials: true}).pipe(map(list => list.map(fromJson))).subscribe(next);
+  }
+
+  postNone(path: any[], data: any, next?: Next<void>): Subscription {
+    return this.http.post<void>(getApiUrl('http', path), data, {withCredentials: true}).subscribe(next);
+  }
+
+  postSingle<T>(path: any[], data: any, fromJson: FromJson<T>, next?: Next<T>): Subscription {
+    return this.http.post<any>(getApiUrl('http', path), data, {withCredentials: true}).pipe(map(fromJson)).subscribe(next);
+  }
+
+  postPage<T>(path: any[], data: any, fromJson: FromJson<T>, next: Next<Page<T>> | undefined = undefined): Subscription {
+    return this.http.post<any>(getApiUrl('http', path), data, {withCredentials: true}).pipe(map(Page.fromJson(fromJson))).subscribe(next);
+  }
+
+  postList<T>(path: any[], data: any, fromJson: FromJson<T>, next: Next<T[]> | undefined = undefined): Subscription {
+    return this.http.post<any[]>(getApiUrl('http', path), data, {withCredentials: true}).pipe(map(list => list.map(fromJson))).subscribe(next);
+  }
+
+}
diff --git a/src/main/angular/src/app/api/common/types.ts b/src/main/angular/src/app/api/common/types.ts
new file mode 100644
index 0000000..f940ccb
--- /dev/null
+++ b/src/main/angular/src/app/api/common/types.ts
@@ -0,0 +1,9 @@
+import {environment} from "../../../environments/environment";
+
+export type FromJson<T> = (json: any) => T;
+
+export type Next<T> = (item: T) => void;
+
+export function getApiUrl(protocol: string, path: any[]): string {
+  return protocol + (environment.secure ? 's' : '') + '://' + environment.host + ':' + environment.port + '/' + environment.base + path.join('/');
+}
diff --git a/src/main/angular/src/app/api/common/validators.ts b/src/main/angular/src/app/api/common/validators.ts
new file mode 100644
index 0000000..51f7696
--- /dev/null
+++ b/src/main/angular/src/app/api/common/validators.ts
@@ -0,0 +1,73 @@
+import {FromJson} from "./types";
+
+export function validateNumber(json: any): number {
+  if (!(typeof json === "number")) {
+    throw new Error("Not a number: " + json + " (" + typeof json + "): " + JSON.stringify(json));
+  }
+  return json;
+}
+
+export function validateNumberOrNull(json: any): number | null {
+  if (json === null || json === undefined) {
+    return null;
+  }
+  return validateNumber(json);
+}
+
+export function validateBoolean(json: any): boolean {
+  if (!(typeof json === "boolean")) {
+    throw new Error("Not a boolean: " + json + " (" + typeof json + "): " + JSON.stringify(json));
+  }
+  return json;
+}
+
+export function validateBooleanOrNull(json: any): boolean | null {
+  if (json === null || json === undefined) {
+    return null;
+  }
+  return validateBoolean(json);
+}
+
+export function validateString(json: any): string {
+  if (!(typeof json === "string")) {
+    throw new Error("Not a string: " + json + " (" + typeof json + "): " + JSON.stringify(json));
+  }
+  return json;
+}
+
+export function validateStringOrNull(json: any): string | null {
+  if (json === null || json === undefined) {
+    return null;
+  }
+  return validateString(json);
+}
+
+export function validateDate(json: any): Date {
+  return new Date(Date.parse(validateString(json)));
+}
+
+export function validateDateOrNull(json: any): Date | null {
+  if (json === null || json === undefined) {
+    return null;
+  }
+  return validateDate(json);
+}
+
+export function validateListIgnoreNullItems<T>(jsonList: any, fromJson: FromJson<T | null>): T[] {
+  return jsonList.map(fromJson).filter((item: T | null) => item !== null);
+}
+
+export function validateList<T>(jsonList: any, fromJson: FromJson<T>): T[] {
+  return jsonList.map(fromJson);
+}
+
+export function validateLocalDateOrNull(json: any): Date | null {
+  if (json === null || json === undefined) {
+    return null;
+  }
+  return validateLocalDate(json);
+}
+
+export function validateLocalDate(json: any): Date {
+  return new Date(validateString(json));
+}
diff --git a/src/main/angular/src/app/api/common/ws.ts b/src/main/angular/src/app/api/common/ws.ts
new file mode 100644
index 0000000..d67bfb9
--- /dev/null
+++ b/src/main/angular/src/app/api/common/ws.ts
@@ -0,0 +1,17 @@
+import {StompService} from "@stomp/ng2-stompjs";
+import {getApiUrl} from "./types";
+
+export function stompServiceFactory() {
+  const stomp = new StompService({
+    url: getApiUrl('ws', ['ws']),
+    debug: false,
+    heartbeat_in: 2000,
+    heartbeat_out: 2000,
+    reconnect_delay: 2000,
+    headers: {},
+  });
+  stomp.connected$.subscribe(_ => console.info("WEBSOCKET CONNECTED"));
+  stomp.webSocketErrors$.subscribe(_ => console.info("WEBSOCKET DISCONNECTED"));
+  stomp.activate();
+  return stomp;
+}
diff --git a/src/main/angular/src/app/api/tools/Numbers/Session/NumbersSession.ts b/src/main/angular/src/app/api/tools/Numbers/Session/NumbersSession.ts
new file mode 100644
index 0000000..cd56d93
--- /dev/null
+++ b/src/main/angular/src/app/api/tools/Numbers/Session/NumbersSession.ts
@@ -0,0 +1,40 @@
+import {UserPublic} from "../../../User/UserPublic";
+import {validateBoolean, validateDate, validateList, validateString} from "../../../common/validators";
+import {AbstractSession} from "../../../Session/AbstractSession";
+
+export class NumbersSession extends AbstractSession {
+
+  static readonly TYPE = 'Numbers';
+
+  static readonly TYPE_DISPLAY_NAME = 'Nummern verteilen';
+
+  constructor(
+    type: string,
+    uuid: string,
+    title: string,
+    owner: UserPublic,
+    created: Date,
+    password: string,
+    users: UserPublic[],
+    initial: boolean,
+  ) {
+    if (type !== NumbersSession.TYPE) {
+      throw new Error();
+    }
+    super(NumbersSession.TYPE, NumbersSession.TYPE_DISPLAY_NAME, uuid, owner, created, title, password, users, initial);
+  }
+
+  static fromJson(json: any): NumbersSession {
+    return new NumbersSession(
+      validateString(json['type']),
+      validateString(json['uuid']),
+      validateString(json['title']),
+      UserPublic.fromJson(json['owner']),
+      validateDate(json['created']),
+      validateString(json['password']),
+      validateList(json['users'], UserPublic.fromJson),
+      validateBoolean(json['initial']),
+    );
+  }
+
+}
diff --git a/src/main/angular/src/app/api/tools/Numbers/Session/numbers-session.service.ts b/src/main/angular/src/app/api/tools/Numbers/Session/numbers-session.service.ts
new file mode 100644
index 0000000..923311f
--- /dev/null
+++ b/src/main/angular/src/app/api/tools/Numbers/Session/numbers-session.service.ts
@@ -0,0 +1,21 @@
+import {Injectable} from '@angular/core';
+import {AbstractSessionService} from "../../../Session/AbstractSessionService";
+import {NumbersSession} from "./NumbersSession";
+import {ApiService} from "../../../common/api.service";
+import {Router} from "@angular/router";
+import {UserService} from "../../../User/user.service";
+
+@Injectable({
+  providedIn: 'root'
+})
+export class NumbersSessionService extends AbstractSessionService<NumbersSession> {
+
+  constructor(
+    api: ApiService,
+    router: Router,
+    userService: UserService
+  ) {
+    super(api, router, userService, ['Numbers'], ['Numbers', 'Session'], NumbersSession.fromJson);
+  }
+
+}
diff --git a/src/main/angular/src/app/app.component.html b/src/main/angular/src/app/app.component.html
index 5149855..622fee5 100644
--- a/src/main/angular/src/app/app.component.html
+++ b/src/main/angular/src/app/app.component.html
@@ -1,5 +1,10 @@
 <div id="mainMenu" *ngIf="menuVisible">
-  <div class="mainMenuItem" routerLinkActive="mainMenuItemActive" routerLink="/Solar">Sonnensystem</div>
+  <div class="mainMenuItem" routerLinkActive="mainMenuItemActive" routerLink="/SolarSystem">Sonnensystem</div>
   <div class="mainMenuItem" routerLinkActive="mainMenuItemActive" routerLink="/VoltageDrop">Spannungsabfall</div>
+  <div class="mainMenuItem" routerLinkActive="mainMenuItemActive" routerLink="/Numbers">{{ NumbersSession.TYPE_DISPLAY_NAME }}</div>
+  <ng-container *ngIf="user !== null">
+    <div class="mainMenuItem mainMenuItemRight" routerLinkActive="mainMenuItemActive" routerLink="/Profile">{{ user.name }}</div>
+    <div class="mainMenuItem mainMenuItemRight" routerLinkActive="mainMenuItemActive" (click)="delete()">Profil löschen</div>
+  </ng-container>
 </div>
 <router-outlet (activate)="onActivate($event)"/>
diff --git a/src/main/angular/src/app/app.component.less b/src/main/angular/src/app/app.component.less
index 5434010..aca454c 100644
--- a/src/main/angular/src/app/app.component.less
+++ b/src/main/angular/src/app/app.component.less
@@ -7,6 +7,12 @@
     border-right: 1px solid black;
   }
 
+  .mainMenuItemRight {
+    float: right;
+    border-left: 1px solid black;
+    border-right: none;
+  }
+
   .mainMenuItemActive {
     background-color: lightskyblue;
   }
diff --git a/src/main/angular/src/app/app.component.ts b/src/main/angular/src/app/app.component.ts
index 7013e4b..4430912 100644
--- a/src/main/angular/src/app/app.component.ts
+++ b/src/main/angular/src/app/app.component.ts
@@ -1,6 +1,10 @@
-import {Component} from '@angular/core';
-import {RouterLink, RouterLinkActive, RouterOutlet} from '@angular/router';
+import {Component, OnDestroy, OnInit} from '@angular/core';
+import {Router, RouterLink, RouterLinkActive, RouterOutlet} from '@angular/router';
 import {NgIf} from "@angular/common";
+import {UserService} from "./api/User/user.service";
+import {NumbersSession} from "./api/tools/Numbers/Session/NumbersSession";
+import {UserPrivate} from "./api/User/UserPrivate";
+import {Subscription} from "rxjs";
 
 @Component({
   selector: 'app-root',
@@ -9,12 +13,42 @@ import {NgIf} from "@angular/common";
   templateUrl: './app.component.html',
   styleUrl: './app.component.less'
 })
-export class AppComponent {
+export class AppComponent implements OnInit, OnDestroy {
+
+  protected readonly NumbersSession = NumbersSession;
+
+  private readonly subscriptions: Subscription[] = [];
 
   protected menuVisible = true;
 
-  onActivate(component: any) {
+  protected user: UserPrivate | null = null;
+
+  constructor(
+    protected readonly router: Router,
+    protected readonly userService: UserService,
+  ) {
+    // -
+  }
+
+  protected onActivate(component: any) {
     this.menuVisible = !("PRINTABLE_ONLY" in component) || !component.PRINTABLE_ONLY;
   }
 
+  ngOnInit(): void {
+    this.subscriptions.push(this.userService.subscribe(user => {
+      if (this.user !== null && user === null) {
+        this.router.navigate(['/']);
+      }
+      this.user = user;
+    }));
+  }
+
+  ngOnDestroy(): void {
+    this.subscriptions.forEach(subscription => subscription.unsubscribe());
+  }
+
+  delete() {
+    this.userService.delete();
+  }
+
 }
diff --git a/src/main/angular/src/app/app.config.ts b/src/main/angular/src/app/app.config.ts
index d143aad..7bde281 100644
--- a/src/main/angular/src/app/app.config.ts
+++ b/src/main/angular/src/app/app.config.ts
@@ -5,6 +5,9 @@ import {routes} from './app.routes';
 import {registerLocaleData} from "@angular/common";
 import localeDe from '@angular/common/locales/de';
 import localeDeExtra from '@angular/common/locales/extra/de';
+import {provideHttpClient} from "@angular/common/http";
+import {stompServiceFactory} from "./api/common/ws";
+import {StompService} from "@stomp/ng2-stompjs";
 
 registerLocaleData(localeDe, 'de-DE', localeDeExtra);
 
@@ -13,5 +16,7 @@ export const appConfig: ApplicationConfig = {
     {provide: LOCALE_ID, useValue: 'de-DE'},
     provideZoneChangeDetection({eventCoalescing: true}),
     provideRouter(routes),
+    provideHttpClient(),
+    {provide: StompService, useFactory: stompServiceFactory},
   ]
 };
diff --git a/src/main/angular/src/app/app.routes.ts b/src/main/angular/src/app/app.routes.ts
index cb04ff1..ba2de12 100644
--- a/src/main/angular/src/app/app.routes.ts
+++ b/src/main/angular/src/app/app.routes.ts
@@ -1,16 +1,28 @@
 import {Routes} from '@angular/router';
-import {SolarSystemComponent} from './solar-system/solar-system.component';
-import {VoltageDropComponent} from "./voltage-drop/voltage-drop.component";
-import {SolarSystemPrintoutComponent} from "./solar-system/printout/solar-system-printout.component";
+import {SolarSystemComponent} from './pages/tools/solar-system/solar-system.component';
+import {VoltageDropComponent} from "./pages/tools/voltage-drop/voltage-drop.component";
+import {SolarSystemPrintoutComponent} from "./pages/tools/solar-system/printout/solar-system-printout.component";
+import {NumbersOverviewComponent} from "./pages/tools/numbers/overview/numbers-overview.component";
+import {ProfileComponent} from "./pages/profile/profile.component";
+import {NumbersSessionComponent} from "./pages/tools/numbers/session/numbers-session.component";
+import {UserComponent} from "./pages/user/user.component";
 
 export const routes: Routes = [
   {path: 'SolarSystemPrintout', component: SolarSystemPrintoutComponent},
   {path: 'SolarSystem', component: SolarSystemComponent},
+
   {path: 'VoltageDrop', component: VoltageDropComponent},
 
+  {path: 'Numbers', component: NumbersOverviewComponent},
+  {path: 'Numbers/Session', component: NumbersSessionComponent},
+
+  {path: 'User', component: UserComponent},
+
+  {path: 'Profile', component: ProfileComponent},
+
   // historic
   {path: 'Solar', redirectTo: '/SolarSystem'},
 
   // fallback
-  {path: '**', redirectTo: '/Solar'},
+  {path: '**', redirectTo: '/SolarSystem'},
 ];
diff --git a/src/main/angular/src/app/pages/profile/profile.component.html b/src/main/angular/src/app/pages/profile/profile.component.html
new file mode 100644
index 0000000..0b35979
--- /dev/null
+++ b/src/main/angular/src/app/pages/profile/profile.component.html
@@ -0,0 +1,5 @@
+<ng-container *ngIf="userService.user !== null">
+  <h1>Profil</h1>
+  <app-text [initial]="userService.user.name" (onChange)="userService.changeName($event)"></app-text>
+  <app-session-list [sessions]="userService.user.sessions"></app-session-list>
+</ng-container>
diff --git a/src/main/angular/src/app/pages/profile/profile.component.less b/src/main/angular/src/app/pages/profile/profile.component.less
new file mode 100644
index 0000000..e69de29
diff --git a/src/main/angular/src/app/pages/profile/profile.component.ts b/src/main/angular/src/app/pages/profile/profile.component.ts
new file mode 100644
index 0000000..13993ea
--- /dev/null
+++ b/src/main/angular/src/app/pages/profile/profile.component.ts
@@ -0,0 +1,29 @@
+import {Component} from '@angular/core';
+import {NgForOf, NgIf} from "@angular/common";
+import {UserService} from "../../api/User/user.service";
+import {FormsModule} from "@angular/forms";
+import {TextComponent} from "../../shared/text/text.component";
+import {SessionListComponent} from "../tools/numbers/shared/session-list/session-list.component";
+
+@Component({
+  selector: 'app-profile',
+  standalone: true,
+  imports: [
+    NgForOf,
+    NgIf,
+    FormsModule,
+    TextComponent,
+    SessionListComponent
+  ],
+  templateUrl: './profile.component.html',
+  styleUrl: './profile.component.less'
+})
+export class ProfileComponent {
+
+  constructor(
+    protected readonly userService: UserService,
+  ) {
+    // -
+  }
+
+}
diff --git a/src/main/angular/src/app/pages/tools/numbers/numbers-common.less b/src/main/angular/src/app/pages/tools/numbers/numbers-common.less
new file mode 100644
index 0000000..6a4f2ac
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/numbers-common.less
@@ -0,0 +1,2 @@
+@import "../../../../tile.less";
+@import "../../user/user.less";
diff --git a/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.html b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.html
new file mode 100644
index 0000000..f237571
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.html
@@ -0,0 +1,25 @@
+<div class="tileContainer">
+
+  <div class="tile" *ngIf="userService.user">
+    <div class="tileInner">
+      <div class="tileTitle">
+        Teilnahmen
+      </div>
+      <div class="tileContent">
+        <app-session-list [sessions]="userService.user.sessions"></app-session-list>
+      </div>
+    </div>
+  </div>
+
+  <div class="tile">
+    <div class="tileInner">
+      <div class="tileTitle">
+        Neues Spiel erstellen
+      </div>
+      <div class="tileContent">
+        <button (click)="create()">+ Neu</button>
+      </div>
+    </div>
+  </div>
+
+</div>
diff --git a/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.less b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.less
new file mode 100644
index 0000000..239147d
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.less
@@ -0,0 +1 @@
+@import "../numbers-common.less";
diff --git a/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.ts b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.ts
new file mode 100644
index 0000000..350bbcf
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/overview/numbers-overview.component.ts
@@ -0,0 +1,32 @@
+import {Component} from '@angular/core';
+import {UserService} from "../../../../api/User/user.service";
+import {DatePipe, NgForOf, NgIf} from "@angular/common";
+import {NumbersSessionService} from "../../../../api/tools/Numbers/Session/numbers-session.service";
+import {SessionListComponent} from "../shared/session-list/session-list.component";
+
+@Component({
+  selector: 'app-numbers-overview',
+  standalone: true,
+  imports: [
+    NgForOf,
+    NgIf,
+    DatePipe,
+    SessionListComponent
+  ],
+  templateUrl: './numbers-overview.component.html',
+  styleUrl: './numbers-overview.component.less'
+})
+export class NumbersOverviewComponent {
+
+  constructor(
+    protected readonly userService: UserService,
+    protected readonly numberSessionService: NumbersSessionService,
+  ) {
+    // -
+  }
+
+  create() {
+    this.numberSessionService.create(session => this.numberSessionService.goto(session));
+  }
+
+}
diff --git a/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.html b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.html
new file mode 100644
index 0000000..e919d0f
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.html
@@ -0,0 +1,38 @@
+<ng-container *ngIf="session !== null">
+  <h1>{{ session.typeDisplayName }}</h1>
+  <table>
+    <tr>
+      <th>Erstellt</th>
+      <td>{{ session.created | date:'yyyy-MM-dd HH:mm' }}</td>
+    </tr>
+    <tr>
+      <th>Titel</th>
+      <td>
+        <app-text *ngIf="userService.owns(session)" [initial]="session.title" (onChange)="changeTitle(session, $event)"></app-text>
+        <ng-container *ngIf="!userService.owns(session)"></ng-container>
+      </td>
+    </tr>
+    <tr>
+      <th>Passwort</th>
+      <td>
+        <app-text *ngIf="userService.owns(session)" [initial]="session.password" (onChange)="changePassword(session, $event)"></app-text>
+        <ng-container *ngIf="!userService.owns(session)"></ng-container>
+      </td>
+    </tr>
+    <tr>
+      <th>Besitzer</th>
+      <td class="user" (click)="userService.goto(session.owner)">{{ session.owner.name }}</td>
+    </tr>
+    <tr>
+      <th>Teilnehmer</th>
+      <td>
+        <div class="user" *ngFor="let user of session.users" (click)="userService.goto(user)">{{ user.name }}</div>
+      </td>
+    </tr>
+  </table>
+</ng-container>
+
+<ng-container *ngIf="uuid && !session && accessDenied">
+  <h1>Passwort</h1>
+  <input type="text" [(ngModel)]="password" (keydown.enter)="join()">
+</ng-container>
diff --git a/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.less b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.less
new file mode 100644
index 0000000..239147d
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.less
@@ -0,0 +1 @@
+@import "../numbers-common.less";
diff --git a/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.ts b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.ts
new file mode 100644
index 0000000..f7757f1
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/session/numbers-session.component.ts
@@ -0,0 +1,76 @@
+import {Component, OnInit} from '@angular/core';
+import {ActivatedRoute, Router} from "@angular/router";
+import {NumbersSession} from "../../../../api/tools/Numbers/Session/NumbersSession";
+import {DatePipe, NgForOf, NgIf} from "@angular/common";
+import {UserService} from "../../../../api/User/user.service";
+import {NumbersSessionService} from "../../../../api/tools/Numbers/Session/numbers-session.service";
+import {FormsModule} from "@angular/forms";
+import {TextComponent} from "../../../../shared/text/text.component";
+
+@Component({
+  selector: 'app-numbers-session',
+  standalone: true,
+  imports: [
+    NgForOf,
+    NgIf,
+    DatePipe,
+    FormsModule,
+    TextComponent
+  ],
+  templateUrl: './numbers-session.component.html',
+  styleUrl: './numbers-session.component.less'
+})
+export class NumbersSessionComponent implements OnInit {
+
+  protected session: NumbersSession | null = null;
+
+  protected uuid: string | null = null;
+
+  protected accessDenied: boolean | null = null;
+
+  protected password: string = "";
+
+  constructor(
+    protected readonly router: Router,
+    protected readonly activatedRoute: ActivatedRoute,
+    protected readonly numbersSessionService: NumbersSessionService,
+    protected readonly userService: UserService,
+  ) {
+    // -
+  }
+
+  ngOnInit(): void {
+    this.password = "";
+    this.accessDenied = null;
+    this.activatedRoute.params.subscribe(params => {
+      this.uuid = params['uuid'];
+      if (this.uuid) {
+        this.numbersSessionService.canAccess(this.uuid, canAccess => {
+          this.accessDenied = !canAccess;
+          if (canAccess && this.uuid) {
+            this.numbersSessionService.get(this.uuid, session => this.setSession(session));
+          }
+        });
+      }
+    });
+  }
+
+  private setSession(session: NumbersSession): void {
+    this.session = session;
+  }
+
+  protected join() {
+    if (this.uuid) {
+      this.numbersSessionService.join(this.uuid, this.password, session => this.setSession(session));
+    }
+  }
+
+  protected changeTitle(session: NumbersSession, title: string) {
+    this.numbersSessionService.changeTitle(session, title, session => this.setSession(session));
+  }
+
+  protected changePassword(session: NumbersSession, password: string) {
+    this.numbersSessionService.changePassword(session, password, session => this.setSession(session));
+  }
+
+}
diff --git a/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.html b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.html
new file mode 100644
index 0000000..8241a78
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.html
@@ -0,0 +1,20 @@
+<table>
+  <tr>
+    <th>Typ</th>
+    <th>Titel</th>
+    <th>Besitzer</th>
+    <th>Erstellt</th>
+    <th>Teilnehmer</th>
+  </tr>
+  <tr *ngFor="let session of sessions" (click)="numbersSessionService.goto(session)">
+    <td>{{ session.typeDisplayName }}</td>
+    <td>{{ session.title }}</td>
+    <td class="user" (click)="userService.goto(session.owner)">{{ session.owner.name }}</td>
+    <td>{{ session.created | date:'yyyy-MM-dd hh:mm' }}</td>
+    <td>
+      <div class="user" *ngFor="let user of session.users" (click)="userService.goto(user)">
+        {{ user.name }}
+      </div>
+    </td>
+  </tr>
+</table>
diff --git a/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.less b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.less
new file mode 100644
index 0000000..38e483e
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.less
@@ -0,0 +1 @@
+@import "../../numbers-common.less";
diff --git a/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.ts b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.ts
new file mode 100644
index 0000000..c63ae8a
--- /dev/null
+++ b/src/main/angular/src/app/pages/tools/numbers/shared/session-list/session-list.component.ts
@@ -0,0 +1,32 @@
+import {Component, Input} from '@angular/core';
+import {UserService} from "../../../../../api/User/user.service";
+import {NumbersSessionService} from "../../../../../api/tools/Numbers/Session/numbers-session.service";
+import {AbstractSession} from "../../../../../api/Session/AbstractSession";
+import {DatePipe, NgForOf} from "@angular/common";
+
+@Component({
+  selector: 'app-session-list',
+  standalone: true,
+  imports: [
+    DatePipe,
+    NgForOf
+  ],
+  templateUrl: './session-list.component.html',
+  styleUrl: './session-list.component.less'
+})
+export class SessionListComponent {
+
+  @Input() sessions!: AbstractSession[];
+
+  constructor(
+    protected readonly userService: UserService,
+    protected readonly numbersSessionService: NumbersSessionService,
+  ) {
+    // -
+  }
+
+  create() {
+    this.numbersSessionService.create(session => this.numbersSessionService.goto(session));
+  }
+
+}
diff --git a/src/main/angular/src/app/solar-system/SOLAR_SYSTEM.ts b/src/main/angular/src/app/pages/tools/solar-system/SOLAR_SYSTEM.ts
similarity index 100%
rename from src/main/angular/src/app/solar-system/SOLAR_SYSTEM.ts
rename to src/main/angular/src/app/pages/tools/solar-system/SOLAR_SYSTEM.ts
diff --git a/src/main/angular/src/app/solar-system/SolarSystemBody.ts b/src/main/angular/src/app/pages/tools/solar-system/SolarSystemBody.ts
similarity index 100%
rename from src/main/angular/src/app/solar-system/SolarSystemBody.ts
rename to src/main/angular/src/app/pages/tools/solar-system/SolarSystemBody.ts
diff --git a/src/main/angular/src/app/solar-system/printout/solar-system-printout.component.html b/src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.html
similarity index 100%
rename from src/main/angular/src/app/solar-system/printout/solar-system-printout.component.html
rename to src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.html
diff --git a/src/main/angular/src/app/solar-system/printout/solar-system-printout.component.less b/src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.less
similarity index 100%
rename from src/main/angular/src/app/solar-system/printout/solar-system-printout.component.less
rename to src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.less
diff --git a/src/main/angular/src/app/solar-system/printout/solar-system-printout.component.ts b/src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.ts
similarity index 96%
rename from src/main/angular/src/app/solar-system/printout/solar-system-printout.component.ts
rename to src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.ts
index 8713e7c..2a9b017 100644
--- a/src/main/angular/src/app/solar-system/printout/solar-system-printout.component.ts
+++ b/src/main/angular/src/app/pages/tools/solar-system/printout/solar-system-printout.component.ts
@@ -3,7 +3,7 @@ import {BODIES, BODIES_PRINT, EARTH, EARTH_MOON, JUPITER, JUPITER_SCALED_DIAMETE
 import {ActivatedRoute, Params} from "@angular/router";
 import {DecimalPipe, NgForOf, NgIf} from "@angular/common";
 import {MIO_KILO, SolarSystemBody} from "../SolarSystemBody";
-import {Unit} from "../../Unit";
+import {Unit} from "../../../../Unit";
 
 function getScale(params: Params) {
   if ('scale' in params) {
@@ -41,12 +41,10 @@ export class SolarSystemPrintoutComponent implements OnInit {
 
   public readonly PRINTABLE_ONLY: boolean = true;
 
-  protected readonly BODIES_PRINT = BODIES_PRINT;
-
-  protected readonly SolarSystemBody = SolarSystemBody;
-
   protected readonly makePaler = makePaler;
 
+  protected readonly BODIES_PRINT = BODIES_PRINT;
+
   protected readonly MIO_KILO = MIO_KILO;
 
   protected readonly EARTH = EARTH;
diff --git a/src/main/angular/src/app/solar-system/solar-system.component.html b/src/main/angular/src/app/pages/tools/solar-system/solar-system.component.html
similarity index 100%
rename from src/main/angular/src/app/solar-system/solar-system.component.html
rename to src/main/angular/src/app/pages/tools/solar-system/solar-system.component.html
diff --git a/src/main/angular/src/app/solar-system/solar-system.component.less b/src/main/angular/src/app/pages/tools/solar-system/solar-system.component.less
similarity index 68%
rename from src/main/angular/src/app/solar-system/solar-system.component.less
rename to src/main/angular/src/app/pages/tools/solar-system/solar-system.component.less
index 2ee3b56..e7d506a 100644
--- a/src/main/angular/src/app/solar-system/solar-system.component.less
+++ b/src/main/angular/src/app/pages/tools/solar-system/solar-system.component.less
@@ -1,13 +1,4 @@
-@import "../../tile.less";
-
-table {
-  width: 100%;
-}
-
-td {
-  white-space: nowrap;
-  border: 0.2em solid white;
-}
+@import "../../../../tile.less";
 
 .name {
   text-align: left;
diff --git a/src/main/angular/src/app/solar-system/solar-system.component.ts b/src/main/angular/src/app/pages/tools/solar-system/solar-system.component.ts
similarity index 96%
rename from src/main/angular/src/app/solar-system/solar-system.component.ts
rename to src/main/angular/src/app/pages/tools/solar-system/solar-system.component.ts
index 1b3d764..a6e71cb 100644
--- a/src/main/angular/src/app/solar-system/solar-system.component.ts
+++ b/src/main/angular/src/app/pages/tools/solar-system/solar-system.component.ts
@@ -3,7 +3,7 @@ import {DecimalPipe, NgForOf} from "@angular/common";
 import {FormsModule} from "@angular/forms";
 import {MIO_KILO, SolarSystemBody} from "./SolarSystemBody";
 import {BODIES, JUPITER, JUPITER_SCALED_DIAMETER} from "./SOLAR_SYSTEM";
-import {applyPrefixUnit, Unit} from "../Unit";
+import {applyPrefixUnit, Unit} from "../../../Unit";
 import {RouterLink} from "@angular/router";
 
 @Component({
diff --git a/src/main/angular/src/app/voltage-drop/voltage-drop.component.html b/src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.html
similarity index 100%
rename from src/main/angular/src/app/voltage-drop/voltage-drop.component.html
rename to src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.html
diff --git a/src/main/angular/src/app/voltage-drop/voltage-drop.component.less b/src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.less
similarity index 85%
rename from src/main/angular/src/app/voltage-drop/voltage-drop.component.less
rename to src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.less
index 3a9d5a9..4642f39 100644
--- a/src/main/angular/src/app/voltage-drop/voltage-drop.component.less
+++ b/src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.less
@@ -1,4 +1,4 @@
-@import "../../tile.less";
+@import "../../../../tile.less";
 
 #VoltageDropInputs {
 
@@ -18,14 +18,14 @@
   }
 
   .shortcuts {
-    padding-top: calc(@space / 2);
+    padding-top: @halfSpace;
     padding-bottom: calc(@space * 2);
 
     .shortcut {
       float: left;
       font-size: 80%;
-      padding: calc(@space / 2) @space;
-      margin-right: calc(@space / 2);
+      padding: @halfSpace @space;
+      margin-right: @halfSpace;
       background-color: lightskyblue;
       border-radius: @space;
     }
diff --git a/src/main/angular/src/app/voltage-drop/voltage-drop.component.ts b/src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.ts
similarity index 100%
rename from src/main/angular/src/app/voltage-drop/voltage-drop.component.ts
rename to src/main/angular/src/app/pages/tools/voltage-drop/voltage-drop.component.ts
diff --git a/src/main/angular/src/app/pages/user/user.component.html b/src/main/angular/src/app/pages/user/user.component.html
new file mode 100644
index 0000000..ea4435c
--- /dev/null
+++ b/src/main/angular/src/app/pages/user/user.component.html
@@ -0,0 +1,4 @@
+<ng-container *ngIf="user !== null">
+  <h2>Benutzer: {{ user.name }}</h2>
+  <app-session-list [sessions]="user.commonSessions"></app-session-list>
+</ng-container>
diff --git a/src/main/angular/src/app/pages/user/user.component.less b/src/main/angular/src/app/pages/user/user.component.less
new file mode 100644
index 0000000..e69de29
diff --git a/src/main/angular/src/app/pages/user/user.component.ts b/src/main/angular/src/app/pages/user/user.component.ts
new file mode 100644
index 0000000..368498f
--- /dev/null
+++ b/src/main/angular/src/app/pages/user/user.component.ts
@@ -0,0 +1,39 @@
+import {Component, OnInit} from '@angular/core';
+import {NgForOf, NgIf} from "@angular/common";
+import {ActivatedRoute} from "@angular/router";
+import {UserService} from "../../api/User/user.service";
+import {SessionListComponent} from "../tools/numbers/shared/session-list/session-list.component";
+import {UserCommon} from "../../api/User/UserCommon";
+
+@Component({
+  selector: 'app-user',
+  standalone: true,
+  imports: [
+    NgForOf,
+    NgIf,
+    SessionListComponent
+  ],
+  templateUrl: './user.component.html',
+  styleUrl: './user.component.less'
+})
+export class UserComponent implements OnInit {
+
+  protected user: UserCommon | null = null;
+
+  constructor(
+    protected readonly activatedRoute: ActivatedRoute,
+    protected readonly userService: UserService,
+  ) {
+    // -
+  }
+
+  ngOnInit(): void {
+    this.activatedRoute.params.subscribe(params => {
+      const uuid = params['uuid'];
+      if (uuid) {
+        this.userService.getCommonByUuid(uuid, user => this.user = user);
+      }
+    });
+  }
+
+}
diff --git a/src/main/angular/src/app/pages/user/user.less b/src/main/angular/src/app/pages/user/user.less
new file mode 100644
index 0000000..06d2f81
--- /dev/null
+++ b/src/main/angular/src/app/pages/user/user.less
@@ -0,0 +1,10 @@
+.user {
+  float: left;
+  padding: @halfSpace;
+  background-color: lightskyblue;
+  border-radius: @halfSpace;
+}
+
+.user:hover {
+  background-color: dodgerblue;
+}
diff --git a/src/main/angular/src/app/shared/text/text.component.html b/src/main/angular/src/app/shared/text/text.component.html
new file mode 100644
index 0000000..a88214f
--- /dev/null
+++ b/src/main/angular/src/app/shared/text/text.component.html
@@ -0,0 +1 @@
+<input [(ngModel)]="model" (focus)="begin()" (blur)="apply()" (keydown.enter)="apply()" (keydown.escape)="abort()">
diff --git a/src/main/angular/src/app/shared/text/text.component.less b/src/main/angular/src/app/shared/text/text.component.less
new file mode 100644
index 0000000..e69de29
diff --git a/src/main/angular/src/app/shared/text/text.component.ts b/src/main/angular/src/app/shared/text/text.component.ts
new file mode 100644
index 0000000..e292164
--- /dev/null
+++ b/src/main/angular/src/app/shared/text/text.component.ts
@@ -0,0 +1,56 @@
+import {Component, EventEmitter, Input, OnInit, Output} from '@angular/core';
+import {FormsModule} from "@angular/forms";
+
+@Component({
+  selector: 'app-text',
+  standalone: true,
+  imports: [
+    FormsModule
+  ],
+  templateUrl: './text.component.html',
+  styleUrl: './text.component.less'
+})
+export class TextComponent implements OnInit {
+
+  private _initial: string = "";
+
+  protected model: string = this._initial;
+
+  protected editing: boolean = false;
+
+  @Output()
+  readonly onChange = new EventEmitter<string>();
+
+  @Input()
+  set initial(value: string) {
+    this._initial = value;
+    if (!this.editing) {
+      this.model = this._initial;
+    }
+  }
+
+  ngOnInit(): void {
+    this.model = this._initial;
+  }
+
+  begin() {
+    this.editing = true;
+  }
+
+  apply() {
+    if (this.model !== this._initial) {
+      this.onChange.emit(this.model);
+    }
+    this.end();
+  }
+
+  abort() {
+    this.model = this._initial;
+    this.end();
+  }
+
+  end() {
+    this.editing = false;
+  }
+
+}
diff --git a/src/main/angular/src/config.less b/src/main/angular/src/config.less
index f71af77..b5b354c 100644
--- a/src/main/angular/src/config.less
+++ b/src/main/angular/src/config.less
@@ -1 +1,2 @@
 @space: 0.5em;
+@halfSpace: calc(@space / 2);
diff --git a/src/main/angular/src/environments/environment.prod.ts b/src/main/angular/src/environments/environment.prod.ts
new file mode 100644
index 0000000..80ad8e9
--- /dev/null
+++ b/src/main/angular/src/environments/environment.prod.ts
@@ -0,0 +1,7 @@
+export const environment = {
+  production: true,
+  host: window.location.host.split(":")[0],
+  port: window.location.port,
+  base: 'Data/',
+  secure: window.location.protocol === "https:",
+};
diff --git a/src/main/angular/src/environments/environment.ts b/src/main/angular/src/environments/environment.ts
new file mode 100644
index 0000000..8b27d93
--- /dev/null
+++ b/src/main/angular/src/environments/environment.ts
@@ -0,0 +1,8 @@
+export const environment = {
+  production: false,
+  host: window.location.host.split(":")[0],
+  port: 8080,
+  base: '',
+  secure: window.location.protocol === "https:",
+};
+
diff --git a/src/main/angular/src/tile.less b/src/main/angular/src/tile.less
index c28a78b..e6f6785 100644
--- a/src/main/angular/src/tile.less
+++ b/src/main/angular/src/tile.less
@@ -1,11 +1,11 @@
 @import "config.less";
 
 .tileContainer {
-  padding: calc(@space / 2);
+  padding: @halfSpace;
 
   .tile {
     width: 100%;
-    padding: calc(@space / 2);
+    padding: @halfSpace;
 
     .tileInner {
       border: 1px solid #ddd;
@@ -14,12 +14,22 @@
 
       .tileTitle {
         font-weight: bold;
-        padding: calc(@space / 2) @space;
+        padding: @halfSpace @space;
         background-color: lightskyblue;
       }
 
       .tileContent {
-        padding: calc(@space / 2);
+        padding: @halfSpace;
+
+        table {
+          width: 100%;
+        }
+
+        td {
+          white-space: nowrap;
+          border: 0.2em solid white;
+        }
+
       }
     }
 
diff --git a/src/main/java/de/ph87/tools/UserArgumentResolver.java b/src/main/java/de/ph87/tools/UserArgumentResolver.java
new file mode 100644
index 0000000..8979476
--- /dev/null
+++ b/src/main/java/de/ph87/tools/UserArgumentResolver.java
@@ -0,0 +1,40 @@
+package de.ph87.tools;
+
+import de.ph87.tools.user.User;
+import jakarta.servlet.http.Cookie;
+import jakarta.servlet.http.HttpServletRequest;
+import lombok.NonNull;
+import org.springframework.core.MethodParameter;
+import org.springframework.stereotype.Component;
+import org.springframework.web.bind.support.WebDataBinderFactory;
+import org.springframework.web.context.request.NativeWebRequest;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.method.support.ModelAndViewContainer;
+
+import java.util.Arrays;
+
+@Component
+public class UserArgumentResolver implements HandlerMethodArgumentResolver {
+
+  public static final String USER_UUID_COOKIE_NAME = "PatrixToolsUserUuid";
+
+  @Override
+  public boolean supportsParameter(@NonNull final MethodParameter parameter) {
+    return parameter.getParameterType() == User.class;
+  }
+
+  @Override
+  public User resolveArgument(@NonNull final MethodParameter parameter, final ModelAndViewContainer mavContainer, @NonNull final NativeWebRequest webRequest, final WebDataBinderFactory binderFactory) {
+    if (!(webRequest instanceof final HttpServletRequest request)) {
+      return null;
+    }
+
+    final String uuid = Arrays.stream(request.getCookies()).filter(cookie -> USER_UUID_COOKIE_NAME.equalsIgnoreCase(cookie.getName())).findFirst().map(Cookie::getValue).orElse(null);
+    if (uuid == null) {
+      return null;
+    }
+
+    return null;
+  }
+
+}
\ No newline at end of file
diff --git a/src/main/java/de/ph87/tools/session/AbstractSession.java b/src/main/java/de/ph87/tools/session/AbstractSession.java
new file mode 100644
index 0000000..5916bc8
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/AbstractSession.java
@@ -0,0 +1,78 @@
+package de.ph87.tools.session;
+
+import de.ph87.tools.user.User;
+import de.ph87.tools.web.IWebSocketMessage;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.Setter;
+import lombok.ToString;
+
+import java.time.ZonedDateTime;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+
+@Getter
+@ToString
+public abstract class AbstractSession implements IWebSocketMessage {
+
+  @NonNull
+  public final String uuid = UUID.randomUUID().toString();
+
+  @NonNull
+  public final User owner;
+
+  @NonNull
+  public final ZonedDateTime created = ZonedDateTime.now();
+
+  @NonNull
+  @ToString.Exclude
+  private final Set<User> users = new HashSet<>();
+
+  @Setter
+  @NonNull
+  public String title = "Spiel ohne Namen";
+
+  @Setter
+  @NonNull
+  @ToString.Exclude
+  private String password = UUID.randomUUID().toString().substring(0, 4);
+
+  @Setter
+  private boolean initial = true;
+
+  @NonNull
+  private ZonedDateTime lastAccess = created;
+
+  protected AbstractSession(@NonNull final User user) {
+    this.owner = user;
+    this.join(user);
+  }
+
+  public void join(@NonNull final User user) {
+    synchronized (uuid) {
+      users.add(user);
+      touch();
+      user.join(this);
+    }
+  }
+
+  public void leave(@NonNull final User user) {
+    synchronized (uuid) {
+      users.remove(user);
+      touch();
+      user.leave(this);
+    }
+  }
+
+  private void touch() {
+    lastAccess = ZonedDateTime.now();
+  }
+
+  @Override
+  public List<Object> getWebsocketTopic() {
+    return List.of("Number", uuid);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/session/AbstractSessionController.java b/src/main/java/de/ph87/tools/session/AbstractSessionController.java
new file mode 100644
index 0000000..c2f61a6
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/AbstractSessionController.java
@@ -0,0 +1,154 @@
+package de.ph87.tools.session;
+
+import de.ph87.tools.user.User;
+import de.ph87.tools.user.UserService;
+import jakarta.annotation.Nullable;
+import jakarta.servlet.http.HttpServletResponse;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.http.HttpStatus;
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.server.ResponseStatusException;
+
+import java.time.ZonedDateTime;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import static de.ph87.tools.UserArgumentResolver.USER_UUID_COOKIE_NAME;
+
+@Slf4j
+@CrossOrigin
+@EnableScheduling
+@RequiredArgsConstructor
+public abstract class AbstractSessionController<SESSION extends AbstractSession> {
+
+  private final Set<SESSION> sessions = new HashSet<>();
+
+  private final UserService userService;
+
+  private final ApplicationEventPublisher applicationEventPublisher;
+
+  private final Class<SESSION> sessionClazz;
+
+  @Scheduled(timeUnit = TimeUnit.MINUTES, initialDelay = 5, fixedRate = 5)
+  public void cleanUp() {
+    final ZonedDateTime deadline = ZonedDateTime.now().minusDays(1);
+    synchronized (sessions) {
+      sessions.removeIf(session -> session.getLastAccess().isBefore(deadline));
+    }
+  }
+
+  @GetMapping("create")
+  public AbstractSessionDto create(@CookieValue(name = USER_UUID_COOKIE_NAME, required = false) @Nullable final String userUuid, @NonNull final HttpServletResponse response) {
+    final User user = userService.getUserByUuidOrElseCreate(userUuid, response);
+
+    final Optional<SESSION> existing = user.getSessions().stream().filter(sessionClazz::isInstance).filter(AbstractSession::isInitial).map(sessionClazz::cast).min(Comparator.comparing(AbstractSession::getCreated));
+    if (existing.isPresent()) {
+      log.info("User wanted to create new Session but found existing: {}", existing);
+      return toDto(existing.get(), user);
+    }
+
+    final SESSION session = create(user);
+    log.info("Session CREATED: {}", session);
+    synchronized (sessions) {
+      sessions.add(session);
+    }
+
+    applicationEventPublisher.publishEvent(session);
+    applicationEventPublisher.publishEvent(user);
+    return toDto(session, user);
+  }
+
+  @PostMapping("canAccess")
+  public boolean canAccess(@CookieValue(name = USER_UUID_COOKIE_NAME, required = false) @Nullable final String userUuid, @RequestBody final String sessionUuid) {
+    if (userUuid == null) {
+      return false;
+    }
+    return userService.findByPrivateUuid(userUuid).flatMap(user -> findUserSession(user, sessionUuid)).isPresent();
+  }
+
+  @PostMapping("get")
+  public AbstractSessionDto get(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @RequestBody final String sessionUuid) {
+    final User user = userService.getByPrivateUuidOrThrow(userUuid);
+    final SESSION session = getUserSession(user, sessionUuid);
+    return toDto(session, user);
+  }
+
+  @PostMapping("join")
+  public AbstractSessionDto join(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @RequestBody final SessionJoinInbound inbound) {
+    final User user = userService.getByPrivateUuidOrThrow(userUuid);
+    final SESSION session = getSessionByUuid(inbound.uuid);
+    if (!session.getPassword().equals(inbound.password)) {
+      log.error("Wrong password: user={}, session={}", user, session);
+      throw new ResponseStatusException(HttpStatus.FORBIDDEN);
+    }
+    session.join(user);
+    applicationEventPublisher.publishEvent(session);
+    applicationEventPublisher.publishEvent(user);
+    return toDto(session, user);
+  }
+
+  @PostMapping("changeTitle")
+  public AbstractSessionDto changeTitle(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @RequestBody final SessionChangeTitleInbound inbound) {
+    final User user = userService.getByPrivateUuidOrThrow(userUuid);
+    final SESSION session = getUserSession(user, inbound.uuid);
+    if (session.owner != user) {
+      throw new ResponseStatusException(HttpStatus.FORBIDDEN);
+    }
+    session.setTitle(inbound.title);
+    applicationEventPublisher.publishEvent(session);
+    return toDto(session, user);
+  }
+
+  @PostMapping("changePassword")
+  public AbstractSessionDto changePassword(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @RequestBody final SessionChangePasswordInbound inbound) {
+    final User user = userService.getByPrivateUuidOrThrow(userUuid);
+    final SESSION session = getUserSession(user, inbound.uuid);
+    if (session.owner != user) {
+      throw new ResponseStatusException(HttpStatus.FORBIDDEN);
+    }
+    session.setPassword(inbound.password);
+    applicationEventPublisher.publishEvent(session);
+    return toDto(session, user);
+  }
+
+  @PostMapping("leave")
+  public void leave(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @RequestBody final String sessionUuid) {
+    final User user = userService.getByPrivateUuidOrThrow(userUuid);
+    final SESSION session = getSessionByUuid(sessionUuid);
+    session.leave(user);
+    applicationEventPublisher.publishEvent(session);
+    applicationEventPublisher.publishEvent(user);
+  }
+
+  @NonNull
+  private SESSION getUserSession(@NonNull final User user, @NonNull final String sessionUuid) {
+    return findUserSession(user, sessionUuid).orElseThrow(() -> new ResponseStatusException(HttpStatus.BAD_REQUEST));
+  }
+
+  @NonNull
+  private Optional<SESSION> findUserSession(@NonNull final User user, @NonNull final String sessionUuid) {
+    return user.getSessions().stream().filter(s -> s.uuid.equals(sessionUuid)).filter(sessionClazz::isInstance).map(sessionClazz::cast).findFirst();
+  }
+
+  @NonNull
+  private SESSION getSessionByUuid(@NonNull final String uuid) {
+    synchronized (sessions) {
+      return sessions.stream().filter(u -> u.getUuid().equals(uuid)).findFirst().orElseThrow(() -> new ResponseStatusException(HttpStatus.BAD_REQUEST));
+    }
+  }
+
+  @NonNull
+  protected abstract SESSION create(@NonNull final User user);
+
+  @NonNull
+  protected abstract AbstractSessionDto toDto(@NonNull final SESSION session, @NonNull final User forUser);
+
+}
diff --git a/src/main/java/de/ph87/tools/session/AbstractSessionDto.java b/src/main/java/de/ph87/tools/session/AbstractSessionDto.java
new file mode 100644
index 0000000..5881d4a
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/AbstractSessionDto.java
@@ -0,0 +1,60 @@
+package de.ph87.tools.session;
+
+import de.ph87.tools.tools.numbers.NumbersSession;
+import de.ph87.tools.tools.numbers.NumbersSessionDto;
+import de.ph87.tools.user.UserPublicDto;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+import java.time.ZonedDateTime;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Getter
+@ToString
+public abstract class AbstractSessionDto {
+
+  @NonNull
+  private final String type;
+
+  @NonNull
+  public final String uuid;
+
+  @NonNull
+  public final String title;
+
+  @NonNull
+  public final ZonedDateTime created;
+
+  @NonNull
+  public final String password;
+
+  @NonNull
+  public final UserPublicDto owner;
+
+  @NonNull
+  public final Set<UserPublicDto> users;
+
+  public final boolean initial;
+
+  protected AbstractSessionDto(@NonNull final AbstractSession session, @NonNull final String type) {
+    this.type = type;
+    this.uuid = session.uuid;
+    this.title = session.title;
+    this.created = session.created;
+    this.password = session.getPassword();
+    this.owner = new UserPublicDto(session.owner);
+    this.users = session.getUsers().stream().map(UserPublicDto::new).collect(Collectors.toSet());
+    this.initial = session.isInitial();
+  }
+
+  @NonNull
+  public static AbstractSessionDto toDto(@NonNull final AbstractSession session) {
+    return switch (session) {
+      case NumbersSession numbersSession -> new NumbersSessionDto(numbersSession);
+      default -> throw new IllegalStateException("No DTO mapping for: " + session);
+    };
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/session/SessionChangePasswordInbound.java b/src/main/java/de/ph87/tools/session/SessionChangePasswordInbound.java
new file mode 100644
index 0000000..4c4b4c4
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/SessionChangePasswordInbound.java
@@ -0,0 +1,19 @@
+package de.ph87.tools.session;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+@Getter
+@ToString
+@AllArgsConstructor
+public class SessionChangePasswordInbound {
+
+  @NonNull
+  public final String uuid;
+
+  @NonNull
+  public final String password;
+
+}
diff --git a/src/main/java/de/ph87/tools/session/SessionChangeTitleInbound.java b/src/main/java/de/ph87/tools/session/SessionChangeTitleInbound.java
new file mode 100644
index 0000000..8a09ae7
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/SessionChangeTitleInbound.java
@@ -0,0 +1,19 @@
+package de.ph87.tools.session;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+@Getter
+@ToString
+@AllArgsConstructor
+public class SessionChangeTitleInbound {
+
+  @NonNull
+  public final String uuid;
+
+  @NonNull
+  public final String title;
+
+}
diff --git a/src/main/java/de/ph87/tools/session/SessionJoinInbound.java b/src/main/java/de/ph87/tools/session/SessionJoinInbound.java
new file mode 100644
index 0000000..969805b
--- /dev/null
+++ b/src/main/java/de/ph87/tools/session/SessionJoinInbound.java
@@ -0,0 +1,19 @@
+package de.ph87.tools.session;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+@Getter
+@ToString
+@AllArgsConstructor
+public class SessionJoinInbound {
+
+  @NonNull
+  public final String uuid;
+
+  @NonNull
+  public final String password;
+
+}
diff --git a/src/main/java/de/ph87/tools/tools/numbers/NumbersController.java b/src/main/java/de/ph87/tools/tools/numbers/NumbersController.java
new file mode 100644
index 0000000..967b5cc
--- /dev/null
+++ b/src/main/java/de/ph87/tools/tools/numbers/NumbersController.java
@@ -0,0 +1,32 @@
+package de.ph87.tools.tools.numbers;
+
+import de.ph87.tools.session.AbstractSessionController;
+import de.ph87.tools.session.AbstractSessionDto;
+import de.ph87.tools.user.User;
+import de.ph87.tools.user.UserService;
+import lombok.NonNull;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("Numbers")
+public class NumbersController extends AbstractSessionController<NumbersSession> {
+
+  public NumbersController(final UserService userService, final ApplicationEventPublisher applicationEventPublisher) {
+    super(userService, applicationEventPublisher, NumbersSession.class);
+  }
+
+  @NonNull
+  @Override
+  protected NumbersSession create(@NonNull final User user) {
+    return new NumbersSession(user);
+  }
+
+  @NonNull
+  @Override
+  protected AbstractSessionDto toDto(@NonNull final NumbersSession session, @NonNull final User forUser) {
+    return new NumbersSessionDto(session);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/tools/numbers/NumbersSession.java b/src/main/java/de/ph87/tools/tools/numbers/NumbersSession.java
new file mode 100644
index 0000000..55e98cb
--- /dev/null
+++ b/src/main/java/de/ph87/tools/tools/numbers/NumbersSession.java
@@ -0,0 +1,13 @@
+package de.ph87.tools.tools.numbers;
+
+import de.ph87.tools.session.AbstractSession;
+import de.ph87.tools.user.User;
+import lombok.NonNull;
+
+public class NumbersSession extends AbstractSession {
+
+  protected NumbersSession(@NonNull final User user) {
+    super(user);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/tools/numbers/NumbersSessionDto.java b/src/main/java/de/ph87/tools/tools/numbers/NumbersSessionDto.java
new file mode 100644
index 0000000..4c0920c
--- /dev/null
+++ b/src/main/java/de/ph87/tools/tools/numbers/NumbersSessionDto.java
@@ -0,0 +1,16 @@
+package de.ph87.tools.tools.numbers;
+
+import de.ph87.tools.session.AbstractSessionDto;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+@Getter
+@ToString(callSuper = true)
+public class NumbersSessionDto extends AbstractSessionDto {
+
+  public NumbersSessionDto(@NonNull final NumbersSession session) {
+    super(session, "Numbers");
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/User.java b/src/main/java/de/ph87/tools/user/User.java
new file mode 100644
index 0000000..39df073
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/User.java
@@ -0,0 +1,62 @@
+package de.ph87.tools.user;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import de.ph87.tools.session.AbstractSession;
+import de.ph87.tools.web.IWebSocketMessage;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.Setter;
+import lombok.ToString;
+
+import java.time.ZonedDateTime;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+
+@Getter
+@ToString
+public class User implements IWebSocketMessage {
+
+  @NonNull
+  public final String privateUuid = UUID.randomUUID().toString();
+
+  @NonNull
+  public final String publicUuid = UUID.randomUUID().toString();
+
+  public final ZonedDateTime created = ZonedDateTime.now();
+
+  @JsonIgnore
+  @ToString.Exclude
+  private final Set<AbstractSession> sessions = new HashSet<>();
+
+  private ZonedDateTime lastAccess = created;
+
+  @Setter
+  @NonNull
+  public String name = "unnamed";
+
+  private void touch() {
+    lastAccess = ZonedDateTime.now();
+  }
+
+  public void join(@NonNull final AbstractSession session) {
+    synchronized (privateUuid) {
+      sessions.add(session);
+      touch();
+    }
+  }
+
+  public void leave(@NonNull final AbstractSession session) {
+    synchronized (privateUuid) {
+      sessions.remove(session);
+      touch();
+    }
+  }
+
+  @Override
+  public List<Object> getWebsocketTopic() {
+    return List.of("User", privateUuid);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/UserCommonDto.java b/src/main/java/de/ph87/tools/user/UserCommonDto.java
new file mode 100644
index 0000000..60579e2
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/UserCommonDto.java
@@ -0,0 +1,34 @@
+package de.ph87.tools.user;
+
+import de.ph87.tools.session.AbstractSessionDto;
+import jakarta.annotation.Nullable;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Getter
+@ToString
+public class UserCommonDto {
+
+  @NonNull
+  public final String publicUuid;
+
+  @NonNull
+  public final String name;
+
+  @NonNull
+  public final Set<AbstractSessionDto> commonSessions;
+
+  public UserCommonDto(@NonNull final User target, @Nullable final User principal) {
+    this.publicUuid = target.getPublicUuid();
+    this.name = target.getName();
+    this.commonSessions = target.getSessions().stream()
+      .filter(session -> session.getUsers().contains(principal))
+      .map(AbstractSessionDto::toDto)
+      .collect(Collectors.toSet());
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/UserController.java b/src/main/java/de/ph87/tools/user/UserController.java
new file mode 100644
index 0000000..93bbace
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/UserController.java
@@ -0,0 +1,44 @@
+package de.ph87.tools.user;
+
+import jakarta.annotation.Nullable;
+import jakarta.servlet.http.HttpServletResponse;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.web.bind.annotation.*;
+
+import static de.ph87.tools.UserArgumentResolver.USER_UUID_COOKIE_NAME;
+
+@Slf4j
+@CrossOrigin
+@RestController
+@RequiredArgsConstructor
+@RequestMapping("User")
+public class UserController {
+
+  private final UserService userService;
+
+  @Nullable
+  @GetMapping("whoAmI")
+  public UserPrivateDto whoAmI(@CookieValue(name = USER_UUID_COOKIE_NAME, required = false) @Nullable final String userUuid, @NonNull final HttpServletResponse response) {
+    return userService.getUserByUuidOrNull(userUuid, response);
+  }
+
+  @GetMapping("delete")
+  public void delete(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @NonNull final HttpServletResponse response) {
+    userService.delete(userUuid, response);
+  }
+
+  @NonNull
+  @PostMapping("changeName")
+  public UserPrivateDto changeName(@CookieValue(name = USER_UUID_COOKIE_NAME) @NonNull final String userUuid, @NonNull @RequestBody final String name) {
+    return userService.changeName(userUuid, name);
+  }
+
+  @NonNull
+  @PostMapping("getCommonByUuid")
+  public UserCommonDto getCommonByUuid(@CookieValue(name = USER_UUID_COOKIE_NAME, required = false) @Nullable final String userUuid, @NonNull @RequestBody final String targetUuid) {
+    return userService.getCommonByUuid(userUuid, targetUuid);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/UserPrivateDto.java b/src/main/java/de/ph87/tools/user/UserPrivateDto.java
new file mode 100644
index 0000000..8a503df
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/UserPrivateDto.java
@@ -0,0 +1,48 @@
+package de.ph87.tools.user;
+
+import de.ph87.tools.session.AbstractSessionDto;
+import jakarta.annotation.Nullable;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+import java.time.ZonedDateTime;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Getter
+@ToString
+public class UserPrivateDto {
+
+  @NonNull
+  public final String publicUuid;
+
+  @NonNull
+  public final String name;
+
+  @NonNull
+  public final String privateUuid;
+
+  @NonNull
+  public final ZonedDateTime created;
+
+  @NonNull
+  private final Set<AbstractSessionDto> sessions;
+
+  public UserPrivateDto(@NonNull final User user) {
+    this.publicUuid = user.getPublicUuid();
+    this.name = user.getName();
+    this.privateUuid = user.privateUuid;
+    this.created = user.created;
+    this.sessions = user.getSessions().stream().map(AbstractSessionDto::toDto).collect(Collectors.toSet());
+  }
+
+  @Nullable
+  public static UserPrivateDto orNull(@Nullable final User user) {
+    if (user == null) {
+      return null;
+    }
+    return new UserPrivateDto(user);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/UserPublicDto.java b/src/main/java/de/ph87/tools/user/UserPublicDto.java
new file mode 100644
index 0000000..38d4d17
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/UserPublicDto.java
@@ -0,0 +1,30 @@
+package de.ph87.tools.user;
+
+import de.ph87.tools.web.IWebSocketMessage;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.ToString;
+
+import java.util.List;
+
+@Getter
+@ToString
+public class UserPublicDto implements IWebSocketMessage {
+
+  @NonNull
+  public final String publicUuid;
+
+  @NonNull
+  public final String name;
+
+  public UserPublicDto(@NonNull final User user) {
+    this.publicUuid = user.getPublicUuid();
+    this.name = user.getName();
+  }
+
+  @Override
+  public List<Object> getWebsocketTopic() {
+    return List.of("User", publicUuid);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/user/UserService.java b/src/main/java/de/ph87/tools/user/UserService.java
new file mode 100644
index 0000000..3569bc2
--- /dev/null
+++ b/src/main/java/de/ph87/tools/user/UserService.java
@@ -0,0 +1,115 @@
+package de.ph87.tools.user;
+
+import jakarta.annotation.Nullable;
+import jakarta.servlet.http.Cookie;
+import jakarta.servlet.http.HttpServletResponse;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.http.HttpStatus;
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.stereotype.Service;
+import org.springframework.web.server.ResponseStatusException;
+
+import java.util.HashSet;
+import java.util.Optional;
+import java.util.Set;
+
+import static de.ph87.tools.UserArgumentResolver.USER_UUID_COOKIE_NAME;
+
+@Slf4j
+@Service
+@EnableScheduling
+@RequiredArgsConstructor
+public class UserService {
+
+  private final ApplicationEventPublisher applicationEventPublisher;
+
+  private final Set<User> users = new HashSet<>();
+
+  @NonNull
+  public User getUserByUuidOrElseCreate(@Nullable final String uuid, @NonNull final HttpServletResponse response) {
+    synchronized (users) {
+      final User user = Optional.ofNullable(uuid).map(this::findByPrivateUuid).filter(Optional::isPresent).map(Optional::get).orElseGet(this::create);
+      writeUserUuidCookie(response, user);
+      return user;
+    }
+  }
+
+  @Nullable
+  public UserPrivateDto getUserByUuidOrNull(@Nullable final String userUuid, final @NonNull HttpServletResponse response) {
+    if (userUuid == null || userUuid.isEmpty()) {
+      return null;
+    }
+    final User user = findByPrivateUuid(userUuid).orElse(null);
+    writeUserUuidCookie(response, user);
+    return UserPrivateDto.orNull(user);
+  }
+
+  public void delete(@NonNull final String userUuid, final @NonNull HttpServletResponse response) {
+    synchronized (users) {
+      final User user = findByPrivateUuid(userUuid).orElseThrow(() -> new ResponseStatusException(HttpStatus.BAD_REQUEST));
+      users.remove(user);
+      log.info("User DELETED: {}", user);
+    }
+    writeUserUuidCookie(response, null);
+  }
+
+  @NonNull
+  public User getByPrivateUuidOrThrow(@NonNull final String uuid) {
+    synchronized (users) {
+      return findByPrivateUuid(uuid).orElseThrow(() -> new ResponseStatusException(HttpStatus.BAD_REQUEST));
+    }
+  }
+
+  @NonNull
+  public User getByPublicUuid(@NonNull final String uuid) {
+    synchronized (users) {
+      return findByPublicUuid(uuid).orElseThrow(() -> new ResponseStatusException(HttpStatus.BAD_REQUEST));
+    }
+  }
+
+  @NonNull
+  public Optional<User> findByPrivateUuid(@NonNull final String uuid) {
+    return users.stream().filter(u -> u.getPrivateUuid().equals(uuid)).findFirst();
+  }
+
+  @NonNull
+  public Optional<User> findByPublicUuid(@NonNull final String uuid) {
+    return users.stream().filter(u -> u.getPublicUuid().equals(uuid)).findFirst();
+  }
+
+  @NonNull
+  private User create() {
+    final User user = new User();
+    users.add(user);
+    log.info("User CREATED: {}", user);
+    return user;
+  }
+
+  private static void writeUserUuidCookie(@NonNull final HttpServletResponse response, @Nullable final User user) {
+    final Cookie userUuidCookie = new Cookie(USER_UUID_COOKIE_NAME, "");
+    if (user != null) {
+      userUuidCookie.setValue(user.privateUuid);
+    }
+    userUuidCookie.setPath("/");
+    response.addCookie(userUuidCookie);
+  }
+
+  @NonNull
+  public UserPrivateDto changeName(@NonNull final String uuid, @NonNull final String name) {
+    final User user = getByPrivateUuidOrThrow(uuid);
+    user.setName(name);
+    applicationEventPublisher.publishEvent(new UserPublicDto(user));
+    return new UserPrivateDto(user);
+  }
+
+  @NonNull
+  public UserCommonDto getCommonByUuid(@Nullable final String principalUuid, @NonNull final String targetUuid) {
+    final User principal = principalUuid == null ? null : findByPrivateUuid(principalUuid).orElse(null);
+    final User target = getByPublicUuid(targetUuid);
+    return new UserCommonDto(target, principal);
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/web/IWebSocketMessage.java b/src/main/java/de/ph87/tools/web/IWebSocketMessage.java
new file mode 100644
index 0000000..59df9f9
--- /dev/null
+++ b/src/main/java/de/ph87/tools/web/IWebSocketMessage.java
@@ -0,0 +1,12 @@
+package de.ph87.tools.web;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+
+import java.util.List;
+
+public interface IWebSocketMessage {
+
+  @JsonIgnore
+  List<Object> getWebsocketTopic();
+
+}
diff --git a/src/main/java/de/ph87/tools/web/WebConfig.java b/src/main/java/de/ph87/tools/web/WebConfig.java
index 7d50fb7..2f818d4 100644
--- a/src/main/java/de/ph87/tools/web/WebConfig.java
+++ b/src/main/java/de/ph87/tools/web/WebConfig.java
@@ -1,24 +1,32 @@
 package de.ph87.tools.web;
 
+import de.ph87.tools.UserArgumentResolver;
 import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.servlet.config.annotation.CorsRegistry;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 import org.springframework.web.servlet.resource.PathResourceResolver;
 
 import java.io.IOException;
+import java.util.List;
 
 @Configuration
 @RequiredArgsConstructor
 public class WebConfig implements WebMvcConfigurer {
 
+  @Override
+  public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
+    argumentResolvers.add(new UserArgumentResolver());
+  }
+
   @Override
   public void addCorsMappings(CorsRegistry registry) {
-    registry.addMapping("/**").allowedOrigins("*").allowedMethods("*");
+    registry.addMapping("/**").allowCredentials(true).allowedOriginPatterns("*").allowedMethods("*");
   }
 
   @Override
diff --git a/src/main/java/de/ph87/tools/web/WebSocketConfig.java b/src/main/java/de/ph87/tools/web/WebSocketConfig.java
new file mode 100644
index 0000000..0912a3d
--- /dev/null
+++ b/src/main/java/de/ph87/tools/web/WebSocketConfig.java
@@ -0,0 +1,35 @@
+package de.ph87.tools.web;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.messaging.simp.config.MessageBrokerRegistry;
+import org.springframework.scheduling.TaskScheduler;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+import org.springframework.web.bind.annotation.CrossOrigin;
+import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
+import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
+import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;
+
+@CrossOrigin
+@Configuration
+@EnableWebSocketMessageBroker
+public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
+
+  public static final String DESTINATION = "";
+
+  @Override
+  public void registerStompEndpoints(StompEndpointRegistry registry) {
+    registry.addEndpoint("/ws").setAllowedOrigins("*");
+  }
+
+  @Override
+  public void configureMessageBroker(MessageBrokerRegistry config) {
+    config.enableSimpleBroker(DESTINATION).setHeartbeatValue(new long[]{2000, 2000}).setTaskScheduler(heartBeatScheduler());
+  }
+
+  @Bean
+  public TaskScheduler heartBeatScheduler() {
+    return new ThreadPoolTaskScheduler();
+  }
+
+}
diff --git a/src/main/java/de/ph87/tools/web/WebSocketService.java b/src/main/java/de/ph87/tools/web/WebSocketService.java
new file mode 100644
index 0000000..cd9e6c7
--- /dev/null
+++ b/src/main/java/de/ph87/tools/web/WebSocketService.java
@@ -0,0 +1,25 @@
+package de.ph87.tools.web;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.event.EventListener;
+import org.springframework.lang.NonNull;
+import org.springframework.messaging.simp.SimpMessageSendingOperations;
+import org.springframework.stereotype.Service;
+
+import java.util.stream.Collectors;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class WebSocketService {
+
+  private final SimpMessageSendingOperations simpMessageSendingOperations;
+
+  @EventListener(IWebSocketMessage.class)
+  public void send(@NonNull final IWebSocketMessage message) {
+    final String topic = message.getWebsocketTopic().stream().map(Object::toString).collect(Collectors.joining("/"));
+    simpMessageSendingOperations.convertAndSend(topic, message);
+  }
+
+}