具有多个端口和多个客户端的服务器

Question

I need a server that listens on multiple ports.

Multiple clients can connect to each port. After connecting, server user can select each one of clients and send a text to it, and client will respond to this text. I used threads for this job, but when when trying to listen on multiple port I get an error that says

"Only one usage of each socket address (protocol/network address/port) is normally permitted".

How to solve this problem, and how can I access a thread after client connect to server and send text to it?

My source code:

private void activeToolStripMenuItem_Click(object sender, EventArgs e)
{
    //for each port entered in list box,make a thread
    if (ListBox1.Items.Count != 0)
    {
        activeToolStripMenuItem.Enabled = false;
        inactiveToolStripMenuItem.Enabled = true;
        for ( i = 0; i < ListBox1.Items.Count; ++i)
        {
            serverThread = new Thread(new ThreadStart(StartServer));
            serverThread.Start();
        }
    }
    else
    {
        MessageBox.Show("You Should Add at least 1 port, to Listening Ports List.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }
}

private void StartServer()
{
    counter = counter + 1;
    string Remote_Host_IP;
    int j = i - 1;
    port = Convert.ToInt32(ListBox1.Items[counter]);
    TcpListener listener = new TcpListener(IPAddress.Any, port);
    listener.Start();
    while (true)
    {
        mainSocket = listener.AcceptSocket();
        // you'll need some more thread stuff down here.
        if (mainSocket.Connected)
        {
            Connected_Num = Connected_Num + 1;

            Remote_Host_IP = mainSocket.RemoteEndPoint.ToString();
            this.Invoke(new MethodInvoker(() => AddConnection(Remote_Host_IP)));
        }
    }
}

Answer 1

Nononono:) You need to pass/signal the port number to the accept() thread at the time of its creation, not by means of some 'counter' in the space of all the threads. Also, you should not read the listbox in non-GUI threads.

Iterate the list and get the port number from the ListBox in the GUI thread event-handler and pass the port number, not the ListBox index, as a creation parameter to the accept threads.

Fix that first and then think about the server user interacting with the clients. You will need some sort of protocol that allows each client/user to identify itself.