Peers now transmit their role before sending file

Program.cs

@@ -9,6 +9,9 @@ namespace p2pcopy
 {
     class Program
     {
+        public static string ReceiverRole = "receiver";
+        public static string SenderRole = "sender";
+
         static void Main(string[] args)
         {
             CommandLineArguments cla = CommandLineArguments.Parse(args);

Receiver.cs

@@ -18,6 +18,16 @@ static internal void Run(UdtSocket conn)
             using (var writer = new BinaryWriter(netStream))
             using (var reader = new BinaryReader(netStream))
             {
+                // transmit your role and check if connected peer has the correct role
+                writer.Write(Program.ReceiverRole);
+                string role = reader.ReadString();
+
+                if (role == Program.ReceiverRole)
+                {
+                    Console.Error.WriteLine("Peers can't have the same role.");
+                    return;
+                }
+
                 string fileName = reader.ReadString();
                 long size = reader.ReadInt64();
 

Sender.cs

@@ -15,6 +15,15 @@ static internal void Run(UdtSocket conn, string file, bool bVerbose)
             using (var reader = new BinaryReader(netStream))
             using (var fileReader = new FileStream(file, FileMode.Open, FileAccess.Read))
             {
+                // transmit your role and check if connected peer has the correct role
+                writer.Write(Program.SenderRole);
+                string role = reader.ReadString();
+                if (role == Program.SenderRole)
+                {
+                    Console.Error.WriteLine("Peers can't have the same role.");
+                    return;
+                }
+
                 long fileSize = new FileInfo(file).Length;
 
                 writer.Write(Path.GetFileName(file));