I’m trying to connect TcpClient (client-side) and TcpListener (server-side) to send (more than one) data stream. I have a problem that I could not solve by reading docs and articles…

This is the method I use to start TcpListener (server-side):

public void StartListener()
{
    System.Net.Sockets.TcpListener listener = new(
        IPAddress.Parse("127.0.0.1"),
        15001);
        
    listener.Start();
    while (listen)
    {
        if (listener.Pending())
        {
            try
            {
                Thread thread = new Thread(() =>
                {
                    using (TcpClient tcpClient = listener.AcceptTcpClient())
                    using (NetworkStream networkStream = tcpClient.GetStream())
                    using (StreamReader streamReader = new StreamReader(networkStream))
                    {
                        string message = streamReader.ReadToEnd();
                            
                        Console.WriteLine("Message: " + message.Length + " bytes");
                    }
                });
                thread.Start();
            }
            catch (SocketException se)
            {
                Console.WriteLine($"{se.Message} ({se.ErrorCode})");
                throw;
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                throw;
            }
        }
        else
        {
            Thread.Sleep(100);
        }
    } 
}

This is the code I use to send streams (client-side):

public void StartTcpClient()
{
    try
    {
        System.Net.Sockets.TcpClient tcpClient = new();

        tcpClient.Connect(
            "127.0.0.1",
            15001);

        NetworkStream networkStream = tcpClient.GetStream();

        byte[] message = "This is and example."u8.ToArray();
        networkStream.Write(message, 0, message.Length);
    }
    catch (Exception e)
    {
        Console.WriteLine(e.Message);
    }
}

My problem is in the line TcpClient tcpClient = listener.AcceptTcpClient(); when I start the client, a connection is established, but listener.AcceptTcpClient() always returns null. No errors or exceptions are thrown;, the code starts the next iteration.

Any idea?