(图1)
C#语言由于其对网络功能良好的支持,特别是内置地支持TCPListener和TCPClient这二个类,使得利用它开发P2P应用程序变得非常容易。下面就是一个使用C#开发的P2P应用的例子:
public MyTcpListener(int port) : base(port){}public void StopMe(){if ( this.Server != null ){this.Server.Close();}}}public class Transfer{MyTcpListener tcpl;public Transfer(){OptionsLoader ol = new OptionsLoader();int port = 8081;if (ol.Port 0){port = ol.Port;}else{port = 8081;}this.tcpl = new MyTcpListener(port);}public void TransferShutdown(){tcpl.StopMe();}public void ListenForPeers(){try{Encoding ASCII = Encoding.ASCII;tcpl.Start();while (true){// 在有连接之前,Accept将处于阻塞状态Socket s = tcpl.AcceptSocket();NetworkStream DataStream = new NetworkStream(s);String filename;Byte[] Buffer = new Byte[256];DataStream.Read(Buffer, 0, 256);filename = Encoding.ASCII.GetString(Buffer);StringBuilder sbFileName = new StringBuilder(filename);StringBuilder sbFileName2 = sbFileName.Replace("", "\");FileStream fs = new FileStream(sbFileName2.ToString(), FileMode.Open, FileAccess.Read);BinaryReader reader = new BinaryReader(fs);byte[] bytes = new byte[1024];int read;while((read = reader.Read(bytes, 0, bytes.Length)) != 0){DataStream.Write(bytes, 0, read);}reader.Close();DataStream.Flush();DataStream.Close();}}catch(SocketException ex){MessageBox.Show(ex.ToString());}}public void DownloadToClient(String server, string remotefilename, string localfilename){try{TcpClient tcpc = new TcpClient();Byte[] read = new Byte[1024];OptionsLoader ol = new OptionsLoader();int port = 0;if (ol.Port 0){port = ol.Port;}else{// 缺省的端口号,可以设置为使用的端口号port = 8081;}// 尝试与服务器连接IPHostEntry IPHost = Dns.Resolve(server);string []aliases = IPHost.Aliases;IPAddress[] addr = IPHost.AddressList;IPEndPoint ep = new IPEndPoint(addr[0], port);tcpc.Connect(ep);// 获得流对象Stream s = tcpc.GetStream();Byte[] b = Encoding.ASCII.GetBytes(remotefilename.ToCharArray());s.Write( b, 0, b.Length );int bytes;FileStream fs = new FileStream(localfilename, FileMode.OpenOrCreate);BinaryWriter w = new BinaryWriter(fs);// 读取流对象,并将其转换为ASCII码while( (bytes = s.Read(read, 0, read.Length)) != 0){w.Write(read, 0, bytes);read = new Byte[1024];}tcpc.Close();w.Close();fs.Close();}catch(Exception ex){throw new Exception(ex.ToString());}}}}