Code ergänzt

arduino/wlan_an_rpi/wlan_an_rpi.ino

     Serial.println();
     Serial.print("Connecting to ");
     Serial.println(SSID);
- 
+    WiFi.mode(WIFI_STA);
     WiFi.begin(SSID, PSK);
  
     while (WiFi.status() != WL_CONNECTED) {
     snprintf (msg, 50, "Alive since %ld milliseconds", millis());
     Serial.print("Publish message: ");
     Serial.println(msg);
-    client.publish("/home/data", "Hello World");
+    client.publish("/home/data", "Hello asdf World");
     delay(5000);
 }