Question

I have a client and a server that I’m trying to get to speak to eachother over my local network (127.0.0.1).

First, I start the ‘server’ application:

public override void StartListening(int port, IPAddress address) {
            listenClient = new TcpListener(address, port);
            listenClient.Start();
            listenDelimiter = new IPEndPoint(address, port);
            if (listenThread != null) listenThread.Abort();
            listenThread = new Thread(new ParameterizedThreadStart(ListenThread));
            listenThread.IsBackground = true;
            listenThread.Start(port);
        }

        public void ListenThread(object o) {
            while (true) {
                try {
                    Socket incomingConnection = listenClient.AcceptSocket();
                    NetworkStream conStream = new NetworkStream(incomingConnection);
                    NetworkConnection nc = new NetworkConnection((incomingConnection.RemoteEndPoint as IPEndPoint).Port, (incomingConnection.RemoteEndPoint as IPEndPoint).Address);
                    Clients.Add(nc);
                    nc.MonitorTCPStream(conStream, this);
                }
                catch (Exception e) {
                    Console.WriteLine("Server has crashed. Networking error: " + e.Message);
                    Console.WriteLine("Will restart in 60 seconds...");
                    Thread.Sleep(60000);
                    StartListening(WORLDMAP_PORT, IPAddress.Any);
                }
            }
        }

Then the ‘client’:

try {
                    if (worldMapConnection != null) worldMapConnection.Close();
                    worldMapConnection = new TcpClient(address.ToString(), port);
                    worldMapConnection.Connect(WORLDMAP_ADDRESS, WORLDMAP_PORT);
                    if (worldMapThread != null) worldMapThread.Abort();
                    worldMapThread = new Thread(new ParameterizedThreadStart(WorldMapListener));
                    worldMapThread.IsBackground = true;
                    worldMapThread.Start();
                    if (Engine.Renderer.GetTopMenu().GetType() == typeof(MenuContainerConnecting)) Engine.Renderer.CloseMenu();
                }
                catch (System.Net.Sockets.SocketException e) {
                    if (Engine.Renderer.GetTopMenu().GetType() == typeof(MenuContainerConnecting)) Engine.Renderer.CloseMenu();
                    switch (e.SocketErrorCode) {
                        case SocketError.AddressAlreadyInUse: {
                                Engine.Renderer.OpenMenu(new MenuContainerNotice("Connection Error", "You already have a copy of the game connected to the game server.", "Okay"));
                            } break;
                        case SocketError.ConnectionRefused: {
                                Engine.Renderer.OpenMenu(new MenuContainerNotice("Connection Error", "The connection was refused by the game server.", "Okay"));
                            } break;
                        case SocketError.HostUnreachable: {
                                Engine.Renderer.OpenMenu(new MenuContainerNotice("Connection Error", "Could not connect to the game server. Check your internet connection.", "Okay"));
                            } break;
                        default: {
                                Engine.Renderer.OpenMenu(new MenuContainerNotice("Connection Error", "Could not connect to the game server. The server may be down for maintenance.", "Okay"));
                            } break;
                    }
                }
                catch (Exception) {
                    if (Engine.Renderer.GetTopMenu().GetType() == typeof(MenuContainerConnecting)) Engine.Renderer.CloseMenu();
                    Engine.Renderer.OpenMenu(new MenuContainerNotice("Connection Error", "Could not connect to the game server. An unknown error has occoured.", "Okay"));
                }

WORLDMAP_ADDRESS is 127.0.0.1. The port used is the same on both applications (8269).

However, when I run the client, it catches a System.Net.Sockets.SocketException, whose message in the debugger is:

“A connect request was made on an already connected socket 127.0.0.1:8269”

I don’t understand this, because my server is using a TcpListener, and the client a TcpClient. Surely this shouldn’t be an issue?

Answer 1

These two lines in the client are redundant:

                worldMapConnection = new TcpClient(address.ToString(), port);
                worldMapConnection.Connect(WORLDMAP_ADDRESS, WORLDMAP_PORT);

Constructing the TcpClient object with an address and port is sufficient to get it to connect.