Telnet服务器：发送和接收数据

Question

I am now trying to make a simple client (using Windows.Forms) which connects to a Telnet server, and is able to send and receive data.

I have managed to connect successfully to the server, but I can't figure out how to send data back to the server. (After that I need to figure out how to receive the response data, but I haven't made it that far yet.)

Here's my current code:

using System;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace MUDClient {
public partial class Form1 : Form {
    const string SERVER_IP = "166.78.5.182";
    const int PORT_NO = 9999;
    NetworkStream nwStream;
    TcpClient client;

    public Form1() {
        InitializeComponent();
    }

    private void btn_connect_Click(object sender, EventArgs e) {
        connectToServer();
    }

    private void btn_disconnect_Click(object sender, EventArgs e) {
        client.Close();
        nwStream.Close();
        rtb_outputWindow.AppendText("\n\nClient: Disconnected.");
    }

    private void outputWindowTextChanged(object sender, EventArgs e) {
        rtb_outputWindow.SelectionStart = rtb_outputWindow.Text.Length;
        rtb_outputWindow.ScrollToCaret();
    }

    private void connectToServer() {
        client = new TcpClient(SERVER_IP, PORT_NO);
        //client.ReceiveTimeout = 7000;
        nwStream = client.GetStream();

        new Thread(() => {
            Thread.CurrentThread.IsBackground = true;
            while (client.Connected) {
                byte[] bytesToRead = new byte[client.ReceiveBufferSize];
                int bytesRead = nwStream.Read(bytesToRead, 0, client.ReceiveBufferSize);
                updateOutputWindow(Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));
            }
        }).Start();
    }

    private void updateOutputWindow(string text) {
        if (InvokeRequired) {
            Invoke(new MethodInvoker(delegate () {
                updateOutputWindow(text);
            }));
        }
        else {
            rtb_outputWindow.AppendText(text);
        }
    }

    private void userSentInput(object sender, KeyEventArgs e) {
        RichTextBox inputField = (RichTextBox)sender;
        string userInput = inputField.Text.Trim();

        if ((e.KeyData == Keys.Enter) && (sender == rtb_inputField)) {
            if (nwStream != null) {
                if (!string.IsNullOrWhiteSpace(userInput)) {
                    byte[] bytesToSend = Encoding.ASCII.GetBytes(userInput);

                    nwStream.Write(bytesToSend, 0, bytesToSend.Length);
                    nwStream.Flush();

                    rtb_inputField.Clear();
                    rtb_inputField.Update();
                }
            }
        }
    }
}
}

My program has two RichTextBoxes (one for user input and one for "server output" aka received data), and two buttons (connect and disconnect).

Clicking the Connect Button runs the connectToServer() method which successfully opens a connection between the server and the client.

To send data I want to type into the RichTextBox (rtb_inputField), and when the user presses Enter the data is sent. This is the part that isn't working. Nothing seems to happen when I press Enter.

EDIT: I updated the code. I've added a continuous connection loop within a new thread. This works because I can see the welcome screen from the server. I still can't send anything to the server, though. And if I click the Disconnect button the program crashes with the Exception "An unhandled exception of type 'System.IO.IOException'" in the continuous loop.

Answer 1

Try flushing the stream after the Write:

nwStream.Flush()

You'll also need to contentiously read by wrapping the reading in a loop

while (client.Connected)
{
    byte[] bytesToRead = new byte[client.ReceiveBufferSize];
    int bytesRead = s.Read(bytesToRead, 0, client.ReceiveBufferSize);
   Console.Write(Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));
}