Added periodical pings of all known units

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)