Sending messages between two clients C#

Question

I have a sever that allows me to connect several clients receive a message from client and send every client a message when it connects. What I'm trying to do is send a message from client to another so all the server is supposed to do is get the message from first client and send to another. How can I do that?

This is the code of the server

class Server 
{ 
    private TcpListener tcpListener; private Thread listenThread;
    public Server()
    {
        this.tcpListener = new TcpListener(IPAddress.Any, 3000);
        this.listenThread = new Thread(new ThreadStart(ListenForClients));
        this.listenThread.Start();
    }

    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 = 0;

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

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

        //message has successfully been received
        ASCIIEncoding encoder = new ASCIIEncoding();

        Console.WriteLine(encoder.GetString(message, 0, bytesRead));

        byte[] buffer = encoder.GetBytes("Hello Client!");

        clientStream.Write(buffer, 0, buffer.Length);
        clientStream.Flush();

        tcpClient.Close();
    }

    static void Main(string[] args)
    {
        new Server();
    }

}

and the client

{
    TcpClient client = new TcpClient();

    IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 3000);

    client.Connect(serverEndPoint);

    NetworkStream clientStream = client.GetStream();

    ASCIIEncoding encoder = new ASCIIEncoding();
    byte[] buffer = encoder.GetBytes("Hello Server!");

    clientStream.Write(buffer, 0, buffer.Length);
    clientStream.Flush();

    //message has successfully been received
    byte[] message = new byte[4096];
    int bytesRead;

    bytesRead = 0;

    try
    {
        //blocks until a client sends a message
        bytesRead = clientStream.Read(message, 0, 4096);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }

    Console.WriteLine(encoder.GetString(message, 0, bytesRead));

    Console.ReadLine();
}

Answer 1

You have to hold the incoming TcpClient objects in memory so that you can send to them later.

Something like:

List<TcpClient> connectedClients = new List<TcpClient>();

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

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

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

Then you can get the client out of the list (or just send to the whole list) normally. You may want to encapsulate the TcpClient into a full-fledged "Client" object so you can keep track of what they send/receive and also send messages to specific clients.