Socket - Java Client, C# Server

Question

I am making a program in 2 parts.

Part 1: C# server-socket Application running on PC, listening for commands, and acts accordingly.

Part 2: Java client-socket application running on phone, that sends a command to the pc, when a button is pressed.

Currently, i can send commands from the client to the server, and its all good. But my problem is this: When i send a specific command to the server, i want the server to reply to the client, and the client to read that reply.

Thing just is, when the client tries to read, it time-outs.

Java client program:

class ClientThread implements Runnable 
{   
    public void run() 
    {
        try 
        {
            Socket socket = new Socket(serverIpAddress, serverPort);
            socket.setSoTimeout(5000);

            while (true) 
            {
                try 
                {
                    PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
                    Log.d("Nicklas", "Out it goes");
                    out.println(Command);

                    if (Command == "CMD:GetOptions<EOF>")
                    {
                        Log.d("Nicklas", "Getting options");
                        try
                        {
                            Log.d("Nicklas", "Line 1");
                            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                            Log.d("Nicklas", "Line 2");
                            String answer = in.readLine();
                            Log.d("Nicklas", "answer = " + answer );
                        }
                        catch (Exception ee)
                        {
                            Log.d("Nicklasasasas", ee.toString());
                        }
                    }
                    break;

                } 

                catch (Exception e) 
                {
                    Log.d("Nicklas", "CAE = " + e.toString());
                    break;

                } 
            }
            socket.close();
        } 
        catch (ConnectException ee)
        {
            Log.d("Nicklas", "Kunne ikke forbinde");

        }
        catch (Exception e) 
        {
            Log.d("Nicklasssssss", e.toString());
        }
    }
}

This is called with:

Thread cThread = new Thread(new ClientThread());
        cThread.start();

And uses the global variable "Command", which will contain different information, depending on what button was pressed.

The program fails on the line "String answer = in.readline();" with the exception "java.net.SocketTimeoutException".

This is the C# Server part of the program:

private void ListenForClients()
    {
        this.tcpListener.Start();

        while (true)
        {
            //blocks until a client has connected to the server
            TcpClient client = this.tcpListener.AcceptTcpClient();

            //create a thread to handle communication
            //with connected client
            Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
            clientThread.Start(client);
        }
    }

    private void HandleClientComm(object client)
    {
        TcpClient tcpClient = (TcpClient)client;
        NetworkStream clientStream = tcpClient.GetStream();

        byte[] message = new byte[4096];
        int bytesRead;

        while (true)
        {
            bytesRead = 0;

            try
            {
                //blocks until a client sends a message
                bytesRead = clientStream.Read(message, 0, 4096);
            }
            catch
            {
                //a socket error has occured
                break;
            }

            if (bytesRead == 0)
            {
                //the client has disconnected from the server
                break;
            }

            //message has successfully been received
            ASCIIEncoding encoder = new ASCIIEncoding();
            //System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead));
            string Input = (encoder.GetString(message, 0, bytesRead));
            Input = Input.Trim();
            object[] obj = new object[1];
            obj[0] = Input;
            if (Input == "CMD:GetOptions<EOF>")
            {
                try
                {
                    byte[] buffer = encoder.GetBytes("CMD:Accepted");
                    clientStream.Write(buffer, 0, buffer.Length);
                    clientStream.Flush();
                    MessageBox.Show("Client program asked for reply");
                }
                catch (Exception e)
                {
                    MessageBox.Show("Oh it no work!: " + e.ToString());
                }
            }
            else
            {
                Udfor(Input);
            }


        }

        tcpClient.Close();
    }

Called with the following, in the Form1()

this.tcpListener = new TcpListener(IPAddress.Any, 4532);
this.listenThread = new Thread(new ThreadStart(ListenForClients));
this.listenThread.Start();

The C# Server seems to work fine, and does show the messagebox "client program asked for reply"

Anyone who can spot the error?

Answer 1

I figured it out! The problem was the C#. When the server sent back the command "CMD:Accepted", it never closed the socket, so the android application had no idea of telling if it was done reading! Closing the socket right after flushing + of course not closing it again if i already did, did the trick!