public struct Message {
 private readonly string userName;
 private readonly string content;
 private readonly DateTime postDate;

 public Message(string userName, string content) {
  this.userName = userName;
  this.content = content;
  this.postDate = DateTime.Now;
 }

 public Message(string content) : this("System", content) { }

 public string UserName {
  get { return userName; }
 }

 public string Content {
  get { return content; }
 }

 public DateTime PostDate {
  get { return postDate; }
 }

 public override string ToString() {
  return String.Format("{0}[{1}]：\r\n{2}\r\n", userName, postDate, content);
 }
 }

public interface IMessageSender {
 bool Connect(IPAddress ip, int port); // 連接到服務(wù)端
 bool SendMessage(Message msg);  // 發(fā)送用戶
 void SignOut();     // 注銷系統(tǒng)
}

public delegate void MessageReceivedEventHandler(string msg); 
 public delegate void ClientConnectedEventHandler(IPEndPoint endPoint);
 public delegate void ConnectionLostEventHandler(string info);

public interface IMessageReceiver {
 event MessageReceivedEventHandler MessageReceived; // 接收到發(fā)來的消息
 event ConnectionLostEventHandler ClientLost;  // 遠程主動斷開連接
 event ClientConnectedEventHandler ClientConnected; // 遠程連接到了本地
 void StartListen();  // 開始偵聽端口
 void StopListen();  // 停止偵聽端口
}

public class Talker {
 private IMessageReceiver receiver;
 private IMessageSender sender;

 public Talker(IMessageReceiver receiver, IMessageSender sender) {
  this.receiver = receiver;
  this.sender = sender;
 }
 }

public class MessageSender : IMessageSender {

 TcpClient client;
 Stream streamToServer;

 // 連接至遠程
 public bool Connect(IPAddress ip, int port) {
  try {
  client = new TcpClient();
  client.Connect(ip, port);
  streamToServer = client.GetStream(); // 獲取連接至遠程的流
  return true;
  } catch {
  return false;
  }
 }

 // 發(fā)送消息
 public bool SendMessage(Message msg) {
  try {
  lock (streamToServer) {
   byte[] buffer = Encoding.Unicode.GetBytes(msg.ToString());
   streamToServer.Write(buffer, 0, buffer.Length);
   return true;
  }
  } catch {
  return false;
  }
 }

 // 注銷
 public void SignOut() {
  if (streamToServer != null)
  streamToServer.Dispose();
  if (client != null)
  client.Close();
 }
 }

public delegate void PortNumberReadyEventHandler(int portNumber);

 public class MessageReceiver : IMessageReceiver {

 public event MessageReceivedEventHandler MessageReceived;
 public event ConnectionLostEventHandler ClientLost;
 public event ClientConnectedEventHandler ClientConnected;

 // 當端口號Ok的時候調(diào)用 -- 需要告訴用戶界面使用了哪個端口號在偵聽
 // 這里是業(yè)務(wù)上體現(xiàn)不出來，在實現(xiàn)中才能體現(xiàn)出來的
 public event PortNumberReadyEventHandler PortNumberReady;

 private Thread workerThread;
 private TcpListener listener;

 public MessageReceiver() {
  ((IMessageReceiver)this).StartListen();
 }

 // 開始偵聽：顯示實現(xiàn)接口
 void IMessageReceiver.StartListen() {
  ThreadStart start = new ThreadStart(ListenThreadMethod);
  workerThread = new Thread(start);
  workerThread.IsBackground = true;
  workerThread.Start();
 }

 // 線程入口方法
 private void ListenThreadMethod() {
  IPAddress localIp = IPAddress.Parse("127.0.0.1");
  listener = new TcpListener(localIp, 0);
  listener.Start();

  // 獲取端口號
 IPEndPoint endPoint = listener.LocalEndpoint as IPEndPoint;
  int portNumber = endPoint.Port;
  if (PortNumberReady != null) {
  PortNumberReady(portNumber); // 端口號已經(jīng)OK，通知用戶界面
 }

  while (true) {
  TcpClient remoteClient;
  try {
   remoteClient = listener.AcceptTcpClient();
  } catch {
   break;
  }
  if (ClientConnected != null) {
   // 連接至本機的遠程端口
  endPoint = remoteClient.Client.RemoteEndPoint as IPEndPoint;
   ClientConnected(endPoint); // 通知用戶界面遠程客戶連接
  }

  Stream streamToClient = remoteClient.GetStream();
  byte[] buffer = new byte[8192];

  while (true) {
   try {
   int bytesRead = streamToClient.Read(buffer, 0, 8192);
   if (bytesRead == 0) {
    throw new Exception("客戶端已斷開連接");
   }
   string msg = Encoding.Unicode.GetString(buffer, 0, bytesRead);

   if (MessageReceived != null) {
    MessageReceived(msg); // 已經(jīng)收到消息
   }
   } catch (Exception ex) {
   if (ClientLost != null) {
    ClientLost(ex.Message); // 客戶連接丟失
   break;   // 退出循環(huán)
   }
   }
  }
  }
 }

 // 停止偵聽端口
 public void StopListen() {
  try {
  listener.Stop();
  listener = null;
  workerThread.Abort();
  } catch { }
 }
 }

public class Talker {
 private IMessageReceiver receiver;
 private IMessageSender sender;

 public Talker(IMessageReceiver receiver, IMessageSender sender) {
  this.receiver = receiver;
  this.sender = sender;
 }

 public Talker() {
  this.receiver = new MessageReceiver();
  this.sender = new MessageSender();
 }

 public event MessageReceivedEventHandler MessageReceived {
  add {
  receiver.MessageReceived += value;
  }
  remove {
  receiver.MessageReceived -= value;
  }
 }

 public event ClientConnectedEventHandler ClientConnected {
  add {
  receiver.ClientConnected += value;
  }
  remove {
  receiver.ClientConnected -= value;
  }
 }

 public event ConnectionLostEventHandler ClientLost {
  add {
  receiver.ClientLost += value;
  }
  remove {
  receiver.ClientLost -= value;
  }
 }

 // 注意這個事件
 public event PortNumberReadyEventHandler PortNumberReady {
  add {
  ((MessageReceiver)receiver).PortNumberReady += value;
  }
  remove {
  ((MessageReceiver)receiver).PortNumberReady -= value;
  }
 }
  

 // 連接遠程 - 使用主機名
 public bool ConnectByHost(string hostName, int port) {
  IPAddress[] ips = Dns.GetHostAddresses(hostName);
  return sender.Connect(ips[0], port);
 }

 // 連接遠程 - 使用IP
 public bool ConnectByIp(string ip, int port) {
  IPAddress ipAddress;
  try {
  ipAddress = IPAddress.Parse(ip);
  } catch {
  return false;
  }
  return sender.Connect(ipAddress, port);
 }


 // 發(fā)送消息
 public bool SendMessage(Message msg) {
  return sender.SendMessage(msg);
 }

 // 釋放資源，停止偵聽
 public void Dispose() {
  try {
  sender.SignOut();
  receiver.StopListen();
  } catch {
  }
 }

 // 注銷
 public void SignOut() {
  try {
  sender.SignOut();
  } catch {
  }
 }
 }

public partial class PrimaryForm : Form {

 private Talker talker;
 private string userName;

 public PrimaryForm(string name) {
  InitializeComponent();
  userName = lbName.Text = name;
  this.talker = new Talker();
  this.Text = userName + " Talking ...";
  talker.ClientLost +=
  new ConnectionLostEventHandler(talker_ClientLost);
  talker.ClientConnected +=
  new ClientConnectedEventHandler(talker_ClientConnected);
  talker.MessageReceived += 
  new MessageReceivedEventHandler(talker_MessageReceived);
  talker.PortNumberReady +=
  new PortNumberReadyEventHandler(PrimaryForm_PortNumberReady);
 }

 void ConnectStatus() { }
 void DisconnectStatus() { }

 // 端口號OK
 void PrimaryForm_PortNumberReady(int portNumber) {  
  PortNumberReadyEventHandler del = delegate(int port) {
  lbPort.Text = port.ToString();
  };
  lbPort.Invoke(del, portNumber);
 }

 // 接收到消息
 void talker_MessageReceived(string msg) {
  MessageReceivedEventHandler del = delegate(string m) {
  txtContent.Text += m;
  };
  txtContent.Invoke(del, msg);
 }

 // 有客戶端連接到本機
 void talker_ClientConnected(IPEndPoint endPoint) {
  ClientConnectedEventHandler del = delegate(IPEndPoint end) {
  IPHostEntry host = Dns.GetHostEntry(end.Address);
  txtContent.Text += 
   String.Format("System[{0}]：\r\n遠程主機{1}連接至本地。\r\n", DateTime.Now, end);
  };
  txtContent.Invoke(del, endPoint);
 }

 // 客戶端連接斷開
 void talker_ClientLost(string info) {
  ConnectionLostEventHandler del = delegate(string information) {
  txtContent.Text +=
   String.Format("System[{0}]：\r\n{1}\r\n", DateTime.Now, information);
  };
  txtContent.Invoke(del, info);
 }

 // 發(fā)送消息
 private void btnSend_Click(object sender, EventArgs e) {
  if (String.IsNullOrEmpty(txtMessage.Text)) {
  MessageBox.Show("請輸入內(nèi)容！");
  txtMessage.Clear();
  txtMessage.Focus();
  return;
  }

  Message msg = new Message(userName, txtMessage.Text);
  if (talker.SendMessage(msg)) {
  txtContent.Text += msg.ToString();
  txtMessage.Clear();
  } else {
  txtContent.Text +=
   String.Format("System[{0}]：\r\n遠程主機已斷開連接\r\n", DateTime.Now);
  DisconnectStatus();
  }
 }


 // 點擊連接
 private void btnConnect_Click(object sender, EventArgs e) {

  string host = txtHost.Text;
  string ip = txtHost.Text;
  int port;

  if (String.IsNullOrEmpty(txtHost.Text)) {
  MessageBox.Show("主機名稱或地址不能為空");
  }  

  try{
  port = Convert.ToInt32(txtPort.Text);
  }catch{
  MessageBox.Show("端口號不能為空，且必須為數(shù)字");
  return;
  }
  
  if (talker.ConnectByHost(host, port)) {
  ConnectStatus();
  txtContent.Text +=
   String.Format("System[{0}]：\r\n已成功連接至遠程\r\n", DateTime.Now);
  return;
  }
  
  if(talker.ConnectByIp(ip, port)){
  ConnectStatus();
  txtContent.Text +=
   String.Format("System[{0}]：\r\n已成功連接至遠程\r\n", DateTime.Now);
  }else{
  MessageBox.Show("遠程主機不存在，或者拒絕連接！");
  }  

  txtMessage.Focus();
 }

 // 關(guān)閉按鈕點按
 private void btnClose_Click(object sender, EventArgs e) {
  try {
  talker.Dispose();
  Application.Exit();
  } catch {
  }
 }

 // 直接點擊右上角的叉
 private void PrimaryForm_FormClosing(object sender, FormClosingEventArgs e) {
  try {
  talker.Dispose();
  Application.Exit();
  } catch {
  }
 }

 // 點擊注銷
 private void btnSignout_Click(object sender, EventArgs e) {
  talker.SignOut();
  DisconnectStatus();
  txtContent.Text += 
  String.Format("System[{0}]：\r\n已經(jīng)注銷\r\n",DateTime.Now);
 }

 private void btnClear_Click(object sender, EventArgs e) {
  txtContent.Clear();
 }
 }