C# Code hangs when trying to read from Network stream

Question

I already tried lots of possible solutions, different types of writing and reading to stream and all that. But I cant seem to get my code to work.

I basically want to simply send a message to localhost:25565 and then read the message back from localhost:25565 with Console.WriteLine();

  public void Connect(String server, String message)
    {
        Int32 port = 25565;
        string localhost = "127.0.0.1";
        IPAddress localAdd = IPAddress.Parse(localhost);
        TcpListener listener = new TcpListener(localAdd, port);
        Console.WriteLine("listening...");
        listener.Start();
        try
        {
            TcpClient client = new TcpClient(server, port);
            client.NoDelay = true;
            NetworkStream stream = client.GetStream();


            if (stream.CanWrite)
             {
                Console.WriteLine("You can write to this NetworkStream.");


                StreamWriter writer = new StreamWriter(client.GetStream());
                writer.Write(message);
                writer.Flush();

            }
             else
             {
                 Console.WriteLine("Sorry.  You cannot write to this NetworkStream.");
             }

             Console.WriteLine("Sent: {0}", message);

             String responseData = String.Empty;

             Console.WriteLine("InBetween test");

             if(stream.CanRead)
             {
                Console.WriteLine("You can read this stream");

                StreamReader reader = new StreamReader(stream);
                string recievedData = reader.ReadToEnd();
                Console.WriteLine(recievedData);

             }
             else
             {
                 Console.WriteLine("Sorry.  You cannot read from this NetworkStream.");
             }

            Console.WriteLine("All completed test");


           stream.Close();
           client.Close();
        }
        catch (ArgumentNullException e)
        {
            Console.WriteLine("ArgumentNullException: {0}", e);
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }

        Console.WriteLine("\n Press Enter to continue...");
        Console.Read();
    }

This is what appears when I debug my app. https://gyazo.com/95464cc4201c98ccd04cac004b0ea540

It stops after You can read this stream.

Thank you in advance for your help.

Answer 1

You are missing the Accept call on the listening server socket.

Below is your example modified to work. The server part is run in a background thread now, so the server and the client can run in parallel.

public class Program
{
    public static readonly int Port = 25565;    
    public static readonly string Localhost = "127.0.0.1";
    public static readonly string Host = "127.0.0.1";

    public static void RunServer()
    {
        // start the server
        IPAddress localAdd = IPAddress.Parse(Localhost);
        TcpListener listener = new TcpListener(localAdd, Port);
        listener.Start();
        Console.WriteLine($"Server: Listening on {localAdd}:{Port}");
        // TODO proper exit from server
        while (true)
        {
            // accept client socket -- note that we handle only one connection at a time
            Socket cliSoc = listener.AcceptSocketAsync().Result;
            Console.WriteLine($"Server: Client socket accepted, from {cliSoc.LocalEndPoint}");
            while (true)
            {
                if (!cliSoc.Connected)
                    break;
                int bufLen = 1000;
                byte[] buf = new byte[bufLen];
                int read = cliSoc.Receive(buf);
                if (read == 0)
                    break;
                string msg = System.Text.Encoding.ASCII.GetString(buf, 0, read);
                Console.WriteLine($"Server: Read from socket: {read} '{msg}'");

                string response = "OK";
                byte[] responseArr = System.Text.Encoding.ASCII.GetBytes(response.ToCharArray());
                int sent = cliSoc.Send(responseArr);
                Console.WriteLine($"Server: sent response ({sent} bytes)");

                cliSoc.Shutdown(SocketShutdown.Both);
            }
            Console.WriteLine($"Server: Client socket closed");
        }
    }

    public static void Connect(string message)
    {
        Task.Run(() => RunServer());

        try
        {
            TcpClient client = new TcpClient();
            client.ConnectAsync(Host, Port).Wait();
            client.NoDelay = true;
            NetworkStream stream = client.GetStream();

            if (stream.CanWrite)
            {
                Console.WriteLine("Client: You can write to this NetworkStream.");

                StreamWriter writer = new StreamWriter(stream);
                writer.Write(message);
                writer.Flush();
                Console.WriteLine($"Client: Wrote to stream ({message}).");
            }
            else
            {
                Console.WriteLine("Client: Sorry.  You cannot write to this NetworkStream.");
            }

            String responseData = String.Empty;

            Console.WriteLine("Client: Reading");

            if(stream.CanRead)
            {
                Console.WriteLine("Client: You can read this stream");

                StreamReader reader = new StreamReader(stream);
                string recievedData = reader.ReadToEnd();
                Console.WriteLine($"Client: Read: {recievedData}");

            }
            else
            {
                Console.WriteLine("Client: Sorry.  You cannot read from this NetworkStream.");
            }

            Console.WriteLine("Client: All completed test");


            stream.Flush();
            //client.Close();
        }
        catch (ArgumentNullException e)
        {
            Console.WriteLine("ArgumentNullException: {0}", e);
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }

        Console.WriteLine("\n Press Enter to continue...");
        Console.Read();
    }

    public static void Main(string[] args)
    {
        Connect("Hi there!");
    }