Form1.cs

using System;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;
using Newtonsoft.Json;

namespace Wetterstation
{
    public partial class Hintergrund : Form
    {
        private MqttClient myClient;
        SettingsModel WeatherstationSettings = new SettingsModel();

        public Hintergrund()
        {
            InitializeComponent();
            WeatherstationSettings = SqliteDataAccess.LoadWeatherstationSettings();
            lbCity.Text = WeatherstationSettings.city;
            
            // Start a timer for date and time
            Timer t = new Timer();
            t.Interval = 1000;
            t.Tick += new EventHandler(this.t_DateTime);
            t.Start();

            mqttStart();
        }
        private void t_DateTime(object sender, EventArgs e)
        {
            lbUhr.Text = DateTime.Now.ToLongTimeString();
            lbDatum.Text = DateTime.Now.ToShortDateString();
        }

        private void LED_Click(object sender, EventArgs e)
        {
        
            System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);
            System.Drawing.Graphics formGraphics;
            formGraphics = this.CreateGraphics();
            formGraphics.FillEllipse(myBrush, new Rectangle(818, 238, 12, 12));
            myBrush.Dispose();
            formGraphics.Dispose();
        }

        private void Label1_Click(object sender, EventArgs e)
        {
            System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);
            System.Drawing.Graphics formGraphics;
            formGraphics = this.CreateGraphics();
            formGraphics.FillEllipse(myBrush, new Rectangle(872, 290, 12, 12));
            myBrush.Dispose();
            formGraphics.Dispose();
        }

        private void LED_S_Click(object sender, EventArgs e)
        {
            System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);
            System.Drawing.Graphics formGraphics;
            formGraphics = this.CreateGraphics();
            formGraphics.FillEllipse(myBrush, new Rectangle(818,350, 12, 12));
            myBrush.Dispose();
            formGraphics.Dispose();
        }

        private void LED_W_Click(object sender, EventArgs e)
        {
            System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);
            System.Drawing.Graphics formGraphics;
            formGraphics = this.CreateGraphics();
            formGraphics.FillEllipse(myBrush, new Rectangle(764, 290, 12, 12));
            myBrush.Dispose();
            formGraphics.Dispose();
        }

        //MQTT connect
        public void mqttStart()
        {
            String topic_publish = "/wetterstation/backend/";
            String topic_subscribe = "/wetterstation/frontend/#";

            System.Console.WriteLine("Hello, World!");
            // Create Client instance
            this.myClient = new MqttClient("mqtt.itstall.de");

            // Register to message received
            myClient.MqttMsgPublishReceived += client_recievedMessage;

            string clientId = Guid.NewGuid().ToString();
            this.myClient.Connect("", "wetterstation", "wetterstation");

            // Subscribe to topic
            this.myClient.Subscribe(new String[] { topic_subscribe }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });

            this.myClient.Publish(topic_publish, Encoding.UTF8.GetBytes("Request_frontend"));
        }

        public void msgPublish(String topic, String message)
        {
            Console.Write("Sending via MQTT: ");
            Console.Write("Topic: " + topic);
            Console.WriteLine("Message: " + message);
            this.myClient.Publish(topic, Encoding.UTF8.GetBytes(message));
        }

        private void client_recievedMessage(object sender, MqttMsgPublishEventArgs e)
        {
            // Handle message received
            var message = System.Text.Encoding.Default.GetString(e.Message);
            System.Console.WriteLine("Message received: " + message);

            this.updateFormWeather(message);
        }

        private void BtSystemKnopf_Click(object sender, EventArgs e)
        {
            Form settings = new Settings();
            // abhängig von Form1
            settings.ShowDialog();
            updateFormComplete();
            this.updateSettings2Mqtt();
        }

        public void updateFormWeather(String message)
        {
            try
            {
                dynamic weatherData = JsonConvert.DeserializeObject(message.ToString());
                lbAussenTemp.Invoke(new Action(() => { lbAussenTemp.Text = weatherData.sensors[1].temperature + " °C"; }));
            }
            catch (Exception ignored) { }
        }

        public void updateFormComplete()
        {
            WeatherstationSettings = SqliteDataAccess.LoadWeatherstationSettings();
            lbCity.Text = WeatherstationSettings.city;
        }

        public void updateSettings2Mqtt()
        {
            Console.WriteLine(JsonConvert.SerializeObject(WeatherstationSettings).ToString());
            this.msgPublish(WeatherstationSettings.mqtt_topic_backend + WeatherstationSettings.frontendId + "/settings", JsonConvert.SerializeObject(WeatherstationSettings).ToString());
        }

        private void Hintergrund_Load(object sender, EventArgs e)
        {

        }
    }
}