java多客户端通信主要使用Socket编程，理论上是通过服务器广播的方式进行通信。
做个例子来实现这个理论，打开服务端后，登录多个客户端，一个客户端发出消息，对所有客户端进行广播。
服务器的主内，主要用于接受多个客户端连接，以及客户端数据
服务器端：
1 package services; 2 3 import java.io.IOException; 4 import java.net.ServerSocket; 5 import java.net.Socket; 6 import java.util.ArrayList; 7 import java.util.List; 8 9 public class Server 10 { 11 12 /** 13 * Author:至尊龙14 */ 15 public static int PORT = 90; 16 public static String HOST = "127.0.0.1"; 17 public static List msg=new ArrayList();18 public static void main(String[] args) 19 { 20 ServerSocket serverSocket = null; 21 Socket socket = null; 22 try 23 { 24 serverSocket = new ServerSocket(PORT); 25 // 等待请求,无请求一直等待 26 while (true) 27 { 28 System.out.println("等待连接"); 29 socket = serverSocket.accept();// 接受请求 30 System.out.println("有连接接接入"); 31 new ThreadedServer(socket); 32 } 33 } 34 catch (Exception e) 35 { 36 try 37 { 38 socket.close(); 39 } 40 catch (IOException e1) 41 { 42 e1.printStackTrace(); 43 } 44 } 45 finally 46 { 47 try 48 { 49 serverSocket.close(); 50 } 51 catch (IOException e) 52 { 53 e.printStackTrace(); 54 } 55 } 56 57 } 58 59 }
服务器端辅助线程
1 package services; 2 3 import java.io.BufferedReader; 4 import java.io.BufferedWriter; 5 import java.io.IOException; 6 import java.io.InputStreamReader; 7 import java.io.OutputStreamWriter; 8 import java.io.PrintWriter; 9 import java.net.Socket; 10 11 public class ThreadedServer extends Thread 12 { 13 14 private Socket socket = null; 15 private BufferedReader br = null; 16 17 PrintWriter pw = null; 18 19 public ThreadedServer(Socket s) 20 { 21 socket = s; 22 try 23 { 24 br = new BufferedReader(new InputStreamReader( 25 socket.getInputStream())); 26 pw = new PrintWriter( 27 new BufferedWriter(new OutputStreamWriter( 28 socket.getOutputStream())), true); 29 start(); 30 } 31 catch (Exception e) 32 { 33 34 e.printStackTrace(); 35 } 36 } 37 38 public void run() 39 { 40 new ReadClientMessage(br, socket);//读取客户端数据 41 while (true)//向客户端发送数据 42 { 43 try 44 { 45 if(Server.msg.size()>0){ 46 for(int i=0;i
客户端：
1 package client; 2 3 import java.io.BufferedReader; 4 import java.io.BufferedWriter; 5 import java.io.IOException; 6 import java.io.InputStreamReader; 7 import java.io.OutputStreamWriter; 8 import java.io.PrintWriter; 9 import java.net.Socket; 10 import java.util.Scanner; 11 12 public class Client 13 { 14 15 /** 16 * Author: 至尊龙 17 * 客户端 18 */ 19 public static void main(String[] args) 20 { 21 Socket socket = null; 22 BufferedReader br = null; 23 PrintWriter pw = null; 24 Scanner scanner = new Scanner(System.in);// 从键盘读取 25 try 26 { 27 // 创建客户端socket 28 socket = new Socket("127.0.0.1", 90); 29 // 读取从客户端发来的消息 30 br = new BufferedReader(new InputStreamReader( 31 socket.getInputStream())); 32 // 写入信息到服务器端 33 pw = new PrintWriter( 34 new BufferedWriter(new OutputStreamWriter( 35 socket.getOutputStream()))); 36 new ReadServerMessage(br);// 从服务器读取消息 37 while (true) 38 { 39 String temp = scanner.nextLine();// 从键盘读取一行 40 pw.println(temp);// 写到服务器 41 pw.flush(); 42 if (temp.equals("q")) 43 break; 44 } 45 } 46 catch (Exception e) 47 { 48 e.printStackTrace(); 49 } 50 finally 51 { 52 try 53 { 54 System.out.println("关闭......"); 55 br.close(); 56 pw.close(); 57 socket.close(); 58 } 59 catch (IOException e) 60 { 61 e.printStackTrace(); 62 } 63 } 64 65 } 66 67 } 68
客户端辅助线程：
1 package client; 2 3 import java.io.BufferedReader; 4 import java.io.IOException; 5 import java.net.Socket; 6 7 public class ReadServerMessage extends Thread 8 { 9 BufferedReader bReader; 10 Socket socket; 11 public ReadServerMessage(BufferedReader br) 12 { 13 this.bReader = br; 14 start(); 15 } 16 17 public void run() 18 { 19 String str = ""; 20 while (true)//一直等待着服务器的消息 21 { 22 try 23 { 24 if(bReader!=null){25 str = bReader.readLine(); 26 if (str.equals("q")) 27 { 28 bReader.close(); 29 socket.close(); 30 break; 31 } 32 }33 } 34 catch (IOException e) 35 { 36 e.printStackTrace(); 37 } 38 System.out.println("Server Message:" + str); 39 } 40 } 41 } 只是简单的实现，如果有更好的方法，欢迎补充。