package com.test.server; import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.IOException;import java.net.ServerSocket;import java.net.Socket; public class Server {  public static void main(String[] args) { new Server().startServer(); }  public void startServer(){ try {  //服務器在9990端口監聽客戶端的連接  ServerSocket ss = new ServerSocket(9999);  System.out.println("server is listening...");  while(true){  //阻塞的accept方法，當一個客戶端連接上，才會返回Socket對象  Socket s = ss.accept();  System.out.println("a client has connected!");  //開啟線程處理通信  new CommunicateThread(s).start();  } } catch (IOException e) {  e.printStackTrace(); } }  public class CommunicateThread extends Thread{  Socket socket; DataInputStream dis; DataOutputStream dos;  public CommunicateThread(Socket socket){  this.socket = socket;  try {  dis = new DataInputStream(socket.getInputStream());  dos = new DataOutputStream(socket.getOutputStream());  } catch (IOException e) {  e.printStackTrace();  } }  @Override public void run() {  super.run();  //讀取客戶端發過來的消息  String msg = null;  try {  while((msg = dis.readUTF()) != null){   System.out.println("client send msg ：" + msg);   String replyMsg = "server reply ： " + msg;   dos.writeUTF(replyMsg);   System.out.println("server reply msg ：" + replyMsg);  }  } catch (IOException e) {  e.printStackTrace();  } } } }

package com.test.client; import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.IOException;import java.net.Socket;import java.util.Scanner; public class Client {  public static void main(String[] args) { new Client().startClient(); }  public void startClient(){ try {  //連接到服務器  Socket socket = new Socket("localhost", 9999);  DataInputStream dis = new DataInputStream(socket.getInputStream());  DataOutputStream dos = new DataOutputStream(socket.getOutputStream());  Scanner scanner = new Scanner(System.in);  String line = null;  listenServerReply(dis);  while((line = scanner.nextLine()) != null){//讀取從鍵盤輸入的一行  dos.writeUTF(line);//發給服務端  System.out.println("client send msg : " + line);  } } catch (Exception e) {  e.printStackTrace(); } }  //監聽服務端回復的消息 public void listenServerReply(final DataInputStream dis){ new Thread(){  @Override  public void run() {  super.run();  String line = null;  try {   while((line = dis.readUTF()) != null){   System.out.println("client receive msg from server: " + line);   }  } catch (IOException e) {   e.printStackTrace();  }  } }.start(); } }