ntp address detection

src/main.cpp

@@ -59,6 +59,10 @@ void serial_read();
 
 void wifi_loop();
 
+void ntp_setup();
+
+uint32_t ip2int(const IPAddress &ip);
+
 void web_index() {
   server.setContentLength(CONTENT_LENGTH_UNKNOWN);
   server.send(200, "text/html", "");
@@ -172,9 +176,8 @@ void wifi_loop() {
   if (!connected) {
     if (hasIp) {
       connected = true;
-      configTime(3600, 3600, WiFi.gatewayIP().toString().c_str());
       Serial.printf("WiFi connected: %s\n", WiFi.localIP().toString().c_str());
-      yield();
+      ntp_setup();
     }
   } else {
     if (!hasIp) {
@@ -184,6 +187,30 @@ void wifi_loop() {
   }
 }
 
+uint32_t ip2int(const IPAddress &ip) {
+  return ((ip[0] * 256 + ip[1]) * 256 + ip[2]) * 256 + ip[3];
+}
+
+void ntp_setup() {
+  char calculatedGateway[16] = {0};
+  uint32_t local = ip2int(WiFi.localIP());
+  uint32_t netmask = ip2int(WiFi.subnetMask());
+  uint32_t gateway = local & netmask + 1;
+  snprintf(
+      calculatedGateway,
+      sizeof(calculatedGateway),
+      "%u.%u.%u.%u",
+      (gateway >> 24) & 0xFF,
+      (gateway >> 16) & 0xFF,
+      (gateway >> 8) & 0xFF,
+      (gateway >> 0) & 0xFF
+  );
+  sntp_set_time_sync_notification_cb(timeSyncCallback);
+  Serial.printf("configTime(%s / %s / %s)\n", WiFi.gatewayIP().toString().c_str(), calculatedGateway, "pool.ntp.org");
+  configTime(3600, 3600, WiFi.gatewayIP().toString().c_str(), calculatedGateway, "pool.ntp.org");
+  yield();
+}
+
 void serial_read() {
   if (Serial.available()) {
     int input = Serial.read();