Added periodical pings of all known units

esp_server/Program.cs

@@ -60,6 +60,8 @@ namespace ESPServer
 		{
 			var unitReceiver = new UnitDataReceiver(config.RootElement.GetProperty("port").GetInt32(), db, registers);
 			unitReceiver.Start();
+			var unitPinger = new UnitPinger(db);
+			unitPinger.Start();
 			var modbusServer = new ModbusServer(registers);
 			modbusServer.Port = config.RootElement.GetProperty("modbusPort").GetInt32();
 			modbusServer.Run();

esp_server/UnitPinger.cs

@@ -0,0 +1,57 @@
+using NLog;
+using System;
+using System.Collections.Generic;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading;
+
+namespace ESPServer
+{
+	class UnitPinger
+	{
+		const int PING_INTERVAL = 30 * 1000; // 30 seconds
+		const int UNIT_TARGET_PORT = 7000;
+
+		private readonly Logger logger = LogManager.GetCurrentClassLogger();
+		UnitsDatabase db;
+
+		public UnitPinger(UnitsDatabase db)
+		{
+			this.db = db;
+		}
+
+		public void Start()
+		{
+			var t = new Thread(new ThreadStart(this.Run));
+			t.Start();
+		}
+
+		private void Run()
+		{
+			logger.Info("Started UnitPinger");
+			while (true)
+			{
+				try
+				{
+					Thread.Sleep(PING_INTERVAL);
+					var ips = db.GetUnitIPs();
+					foreach (var kv in ips)
+					{
+						var ip = kv.Value;
+						using (var udpClient = new UdpClient())
+						{
+							udpClient.Connect(ip, UNIT_TARGET_PORT);
+							var data = Encoding.ASCII.GetBytes("ping");
+							udpClient.Send(data, data.Length);
+							udpClient.Close();
+						}
+					}
+				}
+				catch (Exception e)
+				{
+					logger.Error(e.Message);
+				}
+			}
+		}
+	}
+}

esp_server/UnitsDatabase.cs

@@ -103,6 +103,22 @@ namespace ESPServer
 			}
 		}
 
+		internal Dictionary<string, string> GetUnitIPs()
+		{
+			var result = new Dictionary<string, string>();
+			lock (units)
+			{
+				foreach (var u in units)
+				{
+					if (!string.IsNullOrEmpty(u.ip))
+					{
+						result[u.id] = u.ip;
+					}
+				}
+			}
+			return result;
+		}
+
 		public Unit GetUnit(string id)
 		{
 			lock (units)