本文所述为基于C#实现的多人聊天程序服务端与客户端完整代码。本实例省略了结构定义部分，服务端主要是逻辑处理部分代码，因此使用时需要完善一些窗体按钮之类的。

先看服务端代码如下：

using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Net; using System.Net.Sockets; using System.Threading; namespace 多人聊天程序Server端 { /// <summary> /// 应用程序的主入口点。 /// </summary> [STAThread] static void Main() { Application.Run(new Form1()); } // 启动服务按钮 private void button2_Click(object sender, System.EventArgs e) { try { // 必须填写端口 if(txtPort.Text == "") { MessageBox.Show("请先填写服务端口号!", "提示"); return; } Int32 port = Int32.Parse(txtPort.Text); // 获得端口号 // 创建侦听的Socket mainSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint localEP = new IPEndPoint(IPAddress.Any, port); // 将 Socket 绑定到本地的终结点上 mainSocket.Bind(localEP); // 开始侦听，最大的连接数是 5 mainSocket.Listen(5); // 开始一个异步操作接受客户的连接请求 mainSocket.BeginAccept(new AsyncCallback(OnClientConnect), null); // 启动服务按钮不可用，停止服务按钮可用 UpdateControls(true); } catch(SocketException se) { MessageBox.Show(se.Message, "提示"); } } // 更新“启动服务按钮”和“停止服务”按钮的状态：是否可用； // 注意：两个按钮的状态是互斥的 private void UpdateControls(bool onServe) { button2.Enabled = !onServe; button3.Enabled = onServe; if(onServe) { status.Text = "已启动服务"; } else { status.Text = "未启动服务"; } } // 回调函数，当客户连接上时，将会被调用 public void OnClientConnect(IAsyncResult asyn) { try { // 调用EndAccept完成BeginAccept异步调用，返回一个新的Socket处理与客户的通信 Socket workerSocket = mainSocket.EndAccept(asyn); // 增加客户数目 Interlocked.Increment(ref clientNum); // 将 workerSocket Socket加入到 ArrayList 中 workerSocketList.Add(workerSocket); // 发送欢迎信息给连接上服务器的客户 string msg = "欢迎客户 " + clientNum + " 登录服务器n"; SendWelcomeToClient(msg, clientNum); // 在线客户数目改变，必须更新客户列表 UpdateClientListControl(); // 连接上的客户接收数据 WaitForData(workerSocket, clientNum); // 主 Socket 返回，继续等待其它的连接请求 mainSocket.BeginAccept(new AsyncCallback(OnClientConnect), null); } catch(ObjectDisposedException) { System.Diagnostics.Debugger.Log(0,"1","n OnClientConnection: Socket已经关闭!n"); } catch(SocketException se) { MessageBox.Show(se.Message, "提示"); } } // 发送欢迎信息给客户 void SendWelcomeToClient(string msg, int clientNumber) { // 用UTF8格式来将string信息转化成byte数组形式 byte[] byData = System.Text.Encoding.UTF8.GetBytes(msg); // 获得客户clientNumber对应的Socket Socket workerSocket = (Socket)workerSocketList[clientNumber - 1]; // 将数据发给客户 workerSocket.Send(byData); } // 该类保存当前的socket，它的客户号还有发送给服务器的数据 public class SocketPacket { public System.Net.Sockets.Socket currentSocket; // 当前的Socket public int clientNumber; // 客户号 public byte[] dataBuffer = new byte[1024]; // 发给服务器的数据 // 构造函数 public SocketPacket(System.Net.Sockets.Socket socket, int clientNumber) { currentSocket = socket; this.clientNumber = clientNumber; } } // 开始等待客户发送数据 public void WaitForData(System.Net.Sockets.Socket socket, int clientNumber) { try { if(pfnWorkerCallBack == null) { // 当连接上的客户有写的操作的时候，调用回调函数 pfnWorkerCallBack = new AsyncCallback(OnDataReceived); } SocketPacket socketPacket = new SocketPacket(socket, clientNumber); socket.BeginReceive(socketPacket.dataBuffer, 0, socketPacket.dataBuffer.Length, SocketFlags.None, pfnWorkerCallBack, socketPacket); } catch(SocketException se) { MessageBox.Show (se.Message, "提示"); } } // 当客户写数据时，调用以下方法 public void OnDataReceived(IAsyncResult asyn) { SocketPacket socketData = (SocketPacket)asyn.AsyncState ; try { // EndReceive完成BeginReceive异步调用，返回客户写入流的字节数 int iRx = socketData.currentSocket.EndReceive(asyn); // 加 1 是因为字符串以 '' 作为结束标志符 char[] chars = new char[iRx + 1]; // 对客户发来的信息进行UTF8解码，存入chars字符数组中 System.Text.Decoder decoder = System.Text.Encoding.UTF8.GetDecoder(); int charLen = decoder.GetChars(socketData.dataBuffer, 0, iRx, chars, 0); System.String szData = new System.String(chars); string msg = "客户 " + socketData.clientNumber + " 发的信息:" + szData; // 将客户发的数据加入到信息列表中 AppendToRichEditControl(msg); // 等待数据 WaitForData(socketData.currentSocket, socketData.clientNumber); } catch (ObjectDisposedException ) { System.Diagnostics.Debugger.Log(0,"1","nOnDataReceived: Socket已经关闭!n"); } catch(SocketException se) { if(se.ErrorCode == 10054) { // 将客户断开连接的信息写入信息列表中 string msg = "客户 " + socketData.clientNumber + " 已断开了连接!" + "n"; AppendToRichEditControl(msg); // 移走已关闭的socket workerSocketList[socketData.clientNumber - 1] = null; // 更新客户列表 UpdateClientListControl(); } else { MessageBox.Show (se.Message, "提示"); } } } // 更新信息列表，该方法可由主线程或其他工作线程所调用 private void AppendToRichEditControl(string msg) { // 测试看是哪个线程调用了该方法 if (InvokeRequired) { // We cannot update the GUI on this thread. // All GUI controls are to be updated by the main (GUI) thread. // Hence we will use the invoke method on the control which will // be called when the Main thread is free // Do UI update on UI thread object[] pList = {msg}; txtRecvMsg.BeginInvoke(new UpdateRichEditCallback(OnUpdateRichEdit), pList); } else { // 创建该控件的主线程直接更新信息列表 OnUpdateRichEdit(msg); } } // 添加信息到 txtRecvMsg 中 private void OnUpdateRichEdit(string msg) { // txtRecvMsg.AppendText(msg); txtRecvMsg.Text = txtRecvMsg.Text + msg; } // 更新客户列表 private void UpdateClientListControl() { if (InvokeRequired) // Is this called from a thread other than the one created // the control { clientList.BeginInvoke(new UpdateClientListCallback(UpdateClientList), null); } else { // 创建该控件的主线程直接更新信息列表 UpdateClientList(); } } // 更新客户列表 void UpdateClientList() { clientList.Items.Clear(); // 清空客户列表 for(int i = 0; i < workerSocketList.Count; i++) { // 加1，是因为数组从下标0开始，而我们的客户标号是从1开始 string clientKey = Convert.ToString(i + 1); Socket workerSocket = (Socket)workerSocketList[i]; if(workerSocket != null) { // 将连接着服务器的客户添加到客户列表中 if(workerSocket.Connected) { clientList.Items.Add(clientKey); } } } } // 停止服务按钮 private void button3_Click(object sender, System.EventArgs e) { CloseSockets(); UpdateControls(false); // 更新客户列表 UpdateClientListControl(); } // 发送信息按钮 private void button1_Click(object sender, System.EventArgs e) { // 如果在线客户列表不为空，则允许发送信息 if (clientList.Items.Count != 0 ) { try { string msg = txtSendMsg.Text; msg = "服务器信息: " + msg + "n"; byte[] byData = System.Text.Encoding.UTF8.GetBytes(msg); Socket workerSocket = null; for(int i = 0; i < workerSocketList.Count; i++) { workerSocket = (Socket)workerSocketList[i]; if(workerSocket!= null) { // 发给所有连接上服务器的客户 if(workerSocket.Connected) { workerSocket.Send(byData); } } } } catch(SocketException se) { MessageBox.Show(se.Message, "提示"); } } else { MessageBox.Show("没有在线客户,不能发送信息!", "提示"); } } // 清空信息按钮 private void button4_Click(object sender, System.EventArgs e) { txtRecvMsg.Clear(); // 清空从客户发来的信息 } // 关闭窗体按钮 private void button5_Click(object sender, System.EventArgs e) { CloseSockets(); Close(); } // 关闭Socket void CloseSockets() { // 关闭主Socket if(mainSocket != null) { mainSocket.Close(); } Socket workerSocket = null; // 关闭客户 Socket 数组 for(int i = 0; i < workerSocketList.Count; i++) { workerSocket = (Socket)workerSocketList[i]; if(workerSocket != null) { workerSocket.Close(); workerSocket = null; } } } private void Form1_Load(object sender, System.EventArgs e) { try { // 获得本机的IP地址 txtIP.Text = Dns.Resolve(Dns.GetHostName()).AddressList[0].ToString(); // 启动时，启动服务按钮可用，停止服务按钮不可用 UpdateControls(false); } catch(Exception exc) { MessageBox.Show(exc.Message, "提示"); } } } }

客户端主要实现接收来自服务端返回的消息、实现发送消息的操作界面，创建Socket实例，得到服务器的IP地址，更新控件，连接和断开等，具体代码如下：

using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Net; using System.Net.Sockets; namespace 多人聊天程序Client端 { public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.Label label1; private System.Windows.Forms.TextBox txtIP; private System.Windows.Forms.Label label2; private System.Windows.Forms.Label label3; private System.Windows.Forms.RichTextBox txtSendMsg; private System.Windows.Forms.Label label4; private System.Windows.Forms.Button button1; private System.Windows.Forms.Button button2; private System.Windows.Forms.Button button3; private System.Windows.Forms.Button button4; private System.Windows.Forms.RichTextBox txtRecvMsg; private System.Windows.Forms.TextBox txtPort; private System.Windows.Forms.Button button5; private System.ComponentModel.Container components = null; byte[] m_dataBuffer = new byte[10]; IAsyncResult result; public AsyncCallback pfnCallBack ; private System.Windows.Forms.Label status; private System.Windows.Forms.Label label5; public Socket clientSocket; public Form1() { InitializeComponent(); } private void InitializeComponent() { this.label1 = new System.Windows.Forms.Label(); this.txtIP = new System.Windows.Forms.TextBox(); this.label2 = new System.Windows.Forms.Label(); this.txtPort = new System.Windows.Forms.TextBox(); this.label3 = new System.Windows.Forms.Label(); this.txtSendMsg = new System.Windows.Forms.RichTextBox(); this.label4 = new System.Windows.Forms.Label(); this.status = new System.Windows.Forms.Label(); this.txtRecvMsg = new System.Windows.Forms.RichTextBox(); this.button1 = new System.Windows.Forms.Button(); this.button2 = new System.Windows.Forms.Button(); this.button3 = new System.Windows.Forms.Button(); this.button4 = new System.Windows.Forms.Button(); this.label5 = new System.Windows.Forms.Label(); this.button5 = new System.Windows.Forms.Button(); this.SuspendLayout(); // label1 this.label1.AutoSize = true; this.label1.Location = new System.Drawing.Point(16, 24); this.label1.Name = "label1"; this.label1.Size = new System.Drawing.Size(60, 17); this.label1.TabIndex = 0; this.label1.Text = "服务器IP:"; // txtIP this.txtIP.Location = new System.Drawing.Point(80, 24); this.txtIP.Name = "txtIP"; this.txtIP.Size = new System.Drawing.Size(160, 21); this.txtIP.TabIndex = 1; this.txtIP.Text = ""; // label2 this.label2.AutoSize = true; this.label2.Location = new System.Drawing.Point(16, 56); this.label2.Name = "label2"; this.label2.Size = new System.Drawing.Size(35, 17); this.label2.TabIndex = 2; this.label2.Text = "端口:"; // txtPort this.txtPort.Location = new System.Drawing.Point(80, 56); this.txtPort.Name = "txtPort"; this.txtPort.Size = new System.Drawing.Size(40, 21); this.txtPort.TabIndex = 3; this.txtPort.Text = ""; // label3 this.label3.AutoSize = true; this.label3.Location = new System.Drawing.Point(16, 96); this.label3.Name = "label3"; this.label3.Size = new System.Drawing.Size(110, 17); this.label3.TabIndex = 4; this.label3.Text = "发送信息给服务器:"; // txtSendMsg this.txtSendMsg.Location = new System.Drawing.Point(16, 120); this.txtSendMsg.Name = "txtSendMsg"; this.txtSendMsg.Size = new System.Drawing.Size(224, 88); this.txtSendMsg.TabIndex = 5; this.txtSendMsg.Text = ""; // label4 this.label4.AutoSize = true; this.label4.Location = new System.Drawing.Point(16, 248); this.label4.Name = "label4"; this.label4.Size = new System.Drawing.Size(60, 17); this.label4.TabIndex = 6; this.label4.Text = "连接状态:"; // status this.status.Location = new System.Drawing.Point(80, 248); this.status.Name = "status"; this.status.Size = new System.Drawing.Size(192, 23); this.status.TabIndex = 7; // txtRecvMsg this.txtRecvMsg.Location = new System.Drawing.Point(264, 80); this.txtRecvMsg.Name = "txtRecvMsg"; this.txtRecvMsg.ReadOnly = true; this.txtRecvMsg.Size = new System.Drawing.Size(224, 144); this.txtRecvMsg.TabIndex = 8; this.txtRecvMsg.Text = ""; // button1 this.button1.Location = new System.Drawing.Point(280, 16); this.button1.Name = "button1"; this.button1.Size = new System.Drawing.Size(88, 32); this.button1.TabIndex = 9; this.button1.Text = "连接"; this.button1.Click += new System.EventHandler(this.button1_Click); // button2 this.button2.Location = new System.Drawing.Point(384, 16); this.button2.Name = "button2"; this.button2.Size = new System.Drawing.Size(88, 32); this.button2.TabIndex = 10; this.button2.Text = "断开"; this.button2.Click += new System.EventHandler(this.button2_Click); // button3 this.button3.Location = new System.Drawing.Point(280, 232); this.button3.Name = "button3"; this.button3.Size = new System.Drawing.Size(88, 32); this.button3.TabIndex = 11; this.button3.Text = "清空信息"; this.button3.Click += new System.EventHandler(this.button3_Click); // button4 this.button4.Location = new System.Drawing.Point(384, 232); this.button4.Name = "button4"; this.button4.Size = new System.Drawing.Size(88, 32); this.button4.TabIndex = 12; this.button4.Text = "关闭"; this.button4.Click += new System.EventHandler(this.button4_Click); // label5 this.label5.AutoSize = true; this.label5.Location = new System.Drawing.Point(264, 64); this.label5.Name = "label5"; this.label5.Size = new System.Drawing.Size(134, 17); this.label5.TabIndex = 13; this.label5.Text = "收到服务器发来的信息:"; // button5 this.button5.Location = new System.Drawing.Point(16, 208); this.button5.Name = "button5"; this.button5.Size = new System.Drawing.Size(224, 32); this.button5.TabIndex = 14; this.button5.Text = "发送信息"; this.button5.Click += new System.EventHandler(this.button5_Click); // Form1 this.AutoScaleBaseSize = new System.Drawing.Size(6, 14); this.ClientSize = new System.Drawing.Size(512, 277); this.Controls.Add(this.button5); this.Controls.Add(this.label5); this.Controls.Add(this.button4); this.Controls.Add(this.button3); this.Controls.Add(this.button2); this.Controls.Add(this.button1); this.Controls.Add(this.txtRecvMsg); this.Controls.Add(this.status); this.Controls.Add(this.label4); this.Controls.Add(this.txtSendMsg); this.Controls.Add(this.label3); this.Controls.Add(this.txtPort); this.Controls.Add(this.label2); this.Controls.Add(this.txtIP); this.Controls.Add(this.label1); this.Name = "Form1"; this.Text = "多人聊天程序Client端"; this.Load += new System.EventHandler(this.Form1_Load); this.ResumeLayout(false); } #endregion [STAThread] static void Main() { Application.Run(new Form1()); } // 连接按钮 private void button1_Click(object sender, System.EventArgs e) { // IP地址和端口号不能为空 if(txtIP.Text == "" || txtPort.Text == "") { MessageBox.Show("请先完整填写服务器IP地址和端口号!", "提示"); return; } try { // 创建Socket实例 clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // 得到服务器的IP地址 IPAddress ipAddress = IPAddress.Parse(txtIP.Text); Int32 port = Int32.Parse(txtPort.Text); // 创建远程终结点 IPEndPoint remoteEP = new IPEndPoint(ipAddress, port); // 连接到远程服务器 clientSocket.Connect(remoteEP); if(clientSocket.Connected) { UpdateControls(true); WaitForData(); // 异步等待数据 } } catch(SocketException se) { MessageBox.Show (se.Message, "提示"); UpdateControls(false); } } // 等待数据 public void WaitForData() { try { if(pfnCallBack == null) { // 当连接上的客户有写的操作的时候，调用回调函数 pfnCallBack = new AsyncCallback(OnDataReceived); } SocketPacket socketPacket = new SocketPacket(); socketPacket.thisSocket = clientSocket; result = clientSocket.BeginReceive(socketPacket.dataBuffer, 0, socketPacket.dataBuffer.Length, SocketFlags.None, pfnCallBack, socketPacket); } catch(SocketException se) { MessageBox.Show(se.Message, "提示"); } } // 该类保存Socket以及发送给服务器的数据 public class SocketPacket { public System.Net.Sockets.Socket thisSocket; public byte[] dataBuffer = new byte[1024]; // 发给服务器的数据 } // 接收数据 public void OnDataReceived(IAsyncResult asyn) { try { SocketPacket theSockId = (SocketPacket)asyn.AsyncState ; // EndReceive完成BeginReceive异步调用，返回服务器写入流的字节数 int iRx = theSockId.thisSocket.EndReceive(asyn); // 加 1 是因为字符串以 '' 作为结束标志符 char[] chars = new char[iRx + 1]; // 用UTF8格式来将string信息转化成byte数组形式 System.Text.Decoder decoder = System.Text.Encoding.UTF8.GetDecoder(); int charLen = decoder.GetChars(theSockId.dataBuffer, 0, iRx, chars, 0); System.String szData = new System.String(chars); // 将收到的信息显示在信息列表中 txtRecvMsg.Text = txtRecvMsg.Text + szData; // 等待数据 WaitForData(); } catch (ObjectDisposedException) { System.Diagnostics.Debugger.Log(0,"1","nOnDataReceived: Socket已经关闭!n"); } catch(SocketException se) { if(se.ErrorCode == 10054) { string msg = "服务器" + "停止服务!" + "n"; txtRecvMsg.Text = txtRecvMsg.Text + msg; clientSocket.Close(); clientSocket = null; UpdateControls(false); } else { MessageBox.Show(se.Message, "提示"); } } } // 更新控件。连接和断开（发送信息）按钮的状态是互斥的 private void UpdateControls(bool connected) { button1.Enabled = !connected; button2.Enabled = connected; button5.Enabled = connected; if(connected) { status.Text = "已连接"; } else { status.Text = "无连接"; } } // 断开按钮 private void button2_Click(object sender, System.EventArgs e) { // 关闭Socket if(clientSocket != null) { clientSocket.Close(); clientSocket = null; UpdateControls(false); } } // 发送信息按钮 private void button5_Click(object sender, System.EventArgs e) { try { // 如果客户与服务器有连接，则允许发送信息 if(clientSocket.Connected) { string msg = txtSendMsg.Text + "n"; // 用UTF8格式来将string信息转化成byte数组形式 byte[] byData = System.Text.Encoding.UTF8.GetBytes(msg); if(clientSocket != null) { // 发送数据 clientSocket.Send(byData); } } } catch(Exception se) { MessageBox.Show(se.Message, "提示"); } } // 清空按钮 private void button3_Click(object sender, System.EventArgs e) { txtRecvMsg.Clear(); // 清空信息列表 } // 关闭按钮 private void button4_Click(object sender, System.EventArgs e) { // 关闭Socket if(clientSocket != null) { clientSocket.Close(); clientSocket = null; } Close(); // 关闭窗体 } private void Form1_Load(object sender, System.EventArgs e) { UpdateControls(false); // 初始化时，只有连接按钮可用 } } }