c# - C#中的聊天程序错误

Question

为什么这段代码不起作用？我是 C# 的新手，并从教程中获取了这个。代码中没有错误，但它在调试模式下崩溃。谢谢！

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;

namespace Chat1
{
    public partial class Form1 : Form
    {
        Socket sck;
        EndPoint epLocal, epRemote;
        byte[] buffer;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //Set up socket
            sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

            sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

            //Get User IP

            textLocalIp.Text = GetLocalIp();
            textRemoteIp.Text = GetLocalIp();
        }

        private string GetLocalIp()
        {
            IPHostEntry host;
            host = Dns.GetHostEntry(Dns.GetHostName());
            foreach (IPAddress ip in host.AddressList)
            {
                if (ip.AddressFamily == AddressFamily.InterNetwork)
                    return ip.ToString();
            }

            return "127.0.0.1";
        }

        private void buttonConnect_Click(object sender, EventArgs e)
        {
            // Binding Socket
            epLocal = new IPEndPoint(IPAddress.Parse(textLocalIp.Text), Convert.ToInt32(textLocalPort.Text));
            sck.Bind(epLocal);
            // Connect to Remote IP

            epRemote = new IPEndPoint(IPAddress.Parse(textRemoteIp.Text), Convert.ToInt32(textRemotePort.Text));
            sck.Bind(epRemote); // This is were it directs me when crashing
            //Specific Port

            buffer = new byte[1500];
            sck.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref epRemote, new AsyncCallback(MessageCallBack), buffer);

        }

        private void MessageCallBack(IAsyncResult aResult)
        {
            try
            {
                byte[] recieveData = new byte[1500];
                recieveData = (byte[])aResult.AsyncState;
                //Convert Byte To String
                ASCIIEncoding aEncoding = new ASCIIEncoding();
                string receivedMessage = aEncoding.GetString(recieveData);

                //Adding this item into Textbox

                listMessage.Items.Add("Partner: " + receivedMessage);

                buffer = new byte[1500];
                sck.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref epRemote, new AsyncCallback(MessageCallBack), buffer);
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

        private void buttonSend_Click(object sender, EventArgs e)
        {
            // Convert String to Byte
            ASCIIEncoding aEncoding = new ASCIIEncoding();
            byte[] sendingMessage = new byte[1500];
            sendingMessage = aEncoding.GetBytes(textMessage.Text);

            // Sending the Enconded message
            sck.Send(sendingMessage);
            //Add to the Listbox
            listMessage.Items.Add("Me: " + textMessage.Text);
            textMessage.Text = "";
    }
}

}

Answer 1

您将相同的绑定Socket到多个端点（首先epLocal，然后epRemote）。您需要为epRemote.

例如：

Socket在类的顶部声明两个s：

Socket remoteSocket;
Socket localSocket;

初始化它们Form1_Load：

remoteSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
localSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

在中buttonConnect_Click，将它们绑定到单独的IPEndPoints：

epLocal = new IPEndPoint(IPAddress.Parse(textLocalIp.Text), Convert.ToInt32(textLocalPort.Text));
localSocket.Bind(epLocal);

epRemote = new IPEndPoint(IPAddress.Parse(textRemoteIp.Text), Convert.ToInt32(textRemotePort.Text));
remoteSocket.Bind(epRemote);

由于看起来您正在尝试从远程 IPEndPoint 读取，因此您需要这样做：

buffer = new byte[1500];
remoteSocket.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref epRemote, new AsyncCallback(MessageCallBack), buffer);