如何在java中使用tcp将消息广播到所有客户端

Question

我正在构建一个多线程聊天服务器应用程序，它将广播一个客户端发送给所有客户端的消息。在Internet上的大多数示例和Oracle的网站太广播是使用udp（多播套接字）完成的，但我使用tcp。 有谁知道如何发送消息到所有连接的客户端在TCP连接？ 这里是我当前的代码工作正常，并将从客户端receieved的消息，只有客户端：

EchoServer的

import java.net.*; 
import java.io.*; 

public class EchoServer 
{ 
    public static void main(String[] args) 
     throws IOException 
    { 
     if (args.length != 1) { 
      System.err.println("Usage: java EchoServer <port number>"); 
      System.exit(1); 
     } 

     int portNumber = Integer.parseInt(args[0]); 

     ServerSocket serverSocket = new ServerSocket(Integer.parseInt(args[0])); 

     while (true) { 
      try { 
       Thread t = new Thread(new MultiServer(serverSocket.accept())); 
       t.start(); 
      } catch(IOException e) { 
       System.out.println("Accept Failed:"); 
       System.exit(-1); 
      } 
     } 
    } 
} 

EchoClient

import java.io.*; 
import java.util.Scanner; 
import java.net.*; 

public class EchoClient 
{ 
    public static void main(String[] args) throws IOException 
    { 
     if (args.length != 2) { 
      System.err.println("Usage: java EchoClient <host name><portnumber>"); 
      System.exit(1); 
     } 

     String hostName = "localhost"; 

     int portNumber = Integer.parseInt(args[1]); 

     try (
      Socket echoSocket = new Socket(hostName, portNumber); 
      PrintWriter out = new PrintWriter(echoSocket.getOutputStream(), true); 
      BufferedReader in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream())); 
      BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in)); 
     ) { 
      String userInput; 

      while ((userInput = stdIn.readLine()) != null) { 
       out.println(userInput); 
       System.out.println("echo::" + in.readLine()); 
      } 
     } catch (UnknownHostException e) { 
      System.err.println("Don't know about host " + hostName); 
      System.exit(1); 
     } catch (IOException e) { 
      System.err.println("Couldn't get I/O for the connection to " + hostName); 
      System.exit(1); 
     } 
    } 
} 

多服务器

import java.io.*; 
import java.net.*; 

public class MultiServer implements Runnable 
{ 
    private Socket client; 

    public MultiServer(Socket m) 
    { 
     this.client = m; 
    } 

    @Override 
    public void run() 
    { 
     BufferedReader in = null; 
     PrintWriter out = null; 
     try { 
      out = new PrintWriter(client.getOutputStream(), true); 
      in = new BufferedReader(new InputStreamReader(client.getInputStream())); 
     } catch(IOException ignored) { 
     } 

     while (true) { 
      String line; 
      try { 
       while ((line = in.readLine()) != null) 
        out.println(line); 
      } catch (IOException e) { 
       System.out.println("Read Failed"); 
       System.exit(-1); 
      } 
     } 
    } 
} 

Answer 1

使用并发散列表并维护您的客户端列表。 并发的HashMap是安全的，你将不再需要使用同步，同时增加/迭代/删除

// Create and main list of active clients based on their host name/ip address 
ConcurrentHashMap<String, Socket> activeClients = new ConcurrentHashMap<String, Socket>(); 

// message received 
activeClients.put(clientsocket.getInetAddress().getHostAddress(), clientsocket); 

// broadcast message to all available clients 
for(String clientHost : activeClients.keySet()) { 
     // get each socket here and send a message to them. 
} 

载体基本上是线程安全的一个，所以你不必担心之一。