handlersocketjava里显示，“类没有主方法”

如何干净的实现Android/Java Socket 长连接通信

我们有时候有这种需求，即我们的android客户端要始终保持与服务端的连接，当服务端有任务或消息发送到android客户端的时候就发送，没有任务或消息的时候不发送但要保持这个连接，一旦有任务则开发发送，而我们的android客户端则要保持一个时刻接收任务或消息的状态。

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这个时候我们通过socket来实现这种需求【当然你也可以采用ept，一旦有相应的socket到达，则启动一个线程去处理2:：在线程中处理完返回给我们android客户端的消息或任务之后，要将这种结果表现在ui上，这个步骤方法就比较多了，例如你可以发一个广播来通知ui,或者你可以通过一个static的handler来处理

c#委托的回调 怎么个调?

最典型的应用，就是在异步调用时进行回调，看看MSDN上的例子吧。

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

// State object for reading client data asynchronously public class StateObject { // Client socket. public Socket workSocket = null; // Size of receive buffer. public const int BufferSize = 1024; // Receive buffer. public byte[] buffer = new byte[BufferSize]; // Received data string. public StringBuilder sb = new StringBuilder(); }

public class AsynchronousSocketListener { // Thread signal. public static ManualResetEvent allDone = new ManualResetEvent(false);

public AsynchronousSocketListener() { }

public static void StartListening() { // Data buffer for ing data. byte[] bytes = new Byte[1024];

// Establish the local endpoint for the socket. // The DNS name of puter // running the listener is "". IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName()); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);

// Create a TCP/IP socket. Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp );

// Bind the socket to the local endpoint and listen for ing connections. try { listener.Bind(localEndPoint); listener.Listen(100);

while (true) { // Set the event to nonsignaled state. allDone.Reset();

// Start an asynchronous socket to listen for connections. Console.WriteLine("Waiting for a connection..."); ept( new AsyncCallback(eptCallback), listener );

// Wait until a connection is made before continuing. allDone.WaitOne(); }

} catch (Exception e) { Console.WriteLine(e.ToString()); }

Console.WriteLine(" Press ENTER to continue..."); Console.Read(); }

public static void eptCallback(IAsyncResult ar) { // Signal the main thread to continue. allDone.Set();

// Get the socket that handles the client request. Socket listener = (Socket) ar.AsyncState; Socket handler = ept(ar);

// Create the state object. StateObject state = new StateObject(); state.workSocket = handler; handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); }

public static void ReadCallback(IAsyncResult ar) { String content = String.Empty; // Retrieve the state object and the handler socket // from the asynchronous state object. StateObject state = (StateObject) ar.AsyncState; Socket handler = state.workSocket;

// Read data from the client socket. int bytesRead = handler.EndReceive(ar);

if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString( state.buffer,0,bytesRead));

// Check for end-of-file tag. If it is not there, read // more data. content = state.sb.ToString(); if (content.IndexOf("<EOF>") > -1) { // All the data has been read from the // client. Display it on the console. Console.WriteLine("Read {0} bytes from socket. Data : {1}", content.Length, content ); // Echo the data back to the client. Send(handler, content); } else { // Not all data received. Get more. handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state); } } } private static void Send(Socket handler, String data) { // Convert the string data to byte data using ASCII encoding. byte[] byteData = Encoding.ASCII.GetBytes(data);

// Begin sending the data to the remote device. handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), handler); }

private static void SendCallback(IAsyncResult ar) { try { // Retrieve the socket from the state object. Socket handler = (Socket) ar.AsyncState;

// Complete sending the data to the remote device. int bytesSent = handler.EndSend(ar); Console.WriteLine("Sent {0} bytes to client.", bytesSent);

handler.Shutdown(SocketShutdown.Both); handler.Close();

} catch (Exception e) { Console.WriteLine(e.ToString()); } }

public static int Main(String[] args) { StartListening(); return 0; } }

java里显示，“类没有主方法”

“类没有主方法”是由于程序入口main没有找到！ 在Java中，main()方法是Java应用程序的入口方法，也就是说，程序在运行的时候，第一个执行的方法就是main()方法，这个方法和其他的方法有很大的不同，比如方法的名字必须是main，方法必须是public static void 类型的，方法必须接收一个字符串数组的参数等等。

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