基於udp的服務器消息轉發（羣發）

客戶端通過服務器轉發消息給其他客戶端

轉載地址：http://medicine.iteye.com/blog/1912231
上面實現的是固定ip和端口的客戶端之間的轉發消息，主要是字符串消息。接下來，我對上面的代碼改寫，通過服務器給的ip和端口，客戶端去連接，服務器根據連接的客戶端獲取其ip和端口放進一個list集合裏，最後循環進行轉發。
服務器端

public class Server {
	private static final int SERVER_PORT=1234;//服務器端口
	private static final int BUFFER_SIZE=1024;//緩衝區字節
	private static final List<InetSocketAddress> clientAddressList=new LinkedList<InetSocketAddress>();//用於存放客戶端的ip和端口
	
	public static void main(String[] args) throws IOException {
		System.out.println("服務器已經啓動，監聽端口："+SERVER_PORT);
		int clientPort=0;
		String ip="";
		String str="";
		@SuppressWarnings("resource")
		DatagramSocket socket=new DatagramSocket(SERVER_PORT);
		while(true){
			//從客戶端接收到的內容（客戶端請求）
			DatagramPacket packet=new DatagramPacket(new byte[BUFFER_SIZE],0, BUFFER_SIZE);
			SocketAddress socketAddress=null;
			InetSocketAddress inetSocketAddress=null;
			socket.receive(packet);//接收客戶端數據包
			String msg=new String(packet.getData(),0,packet.getLength());//數據包數據轉爲字符串
			System.out.println("收到客戶端消息："+msg);
			socketAddress=packet.getSocketAddress();//由連接的客戶端數據包來獲得客戶端socket地址
			inetSocketAddress=(InetSocketAddress) socketAddress;
			clientPort=inetSocketAddress.getPort();//獲得連接的客戶端端口號
			ip=inetSocketAddress.getAddress().getHostAddress();//獲得連接的客戶端ip地址
			if(msg.startsWith("getIp")){//利用接收到getIp字符串來獲取客戶端ip和端口
				clientAddressList.add(new InetSocketAddress(ip,clientPort));//將客戶端ip和端口放到一個list集合，爲後面做轉發準備
				str=ip+":"+clientPort;
				byte buff[]=str.getBytes();
				packet.setData(buff,0,buff.length);
				socket.send(packet);//把連接的客戶端ip和端口號發送回給客戶端，表示兩者聯通
				System.out.println(ip+":"+clientPort);
			}
			if("shutdown server".equals(msg)){
				System.out.println("服務器已經被關閉！");//客戶端輸入shutdown server來關閉服務器
				break;
			}else{
				//clientAddressList.remove(new InetSocketAddress(ip,clientPort));
				sendToClients(msg, packet.getSocketAddress());
			}
			
		}
	}
	//服務器向所有客戶端羣發消息
	private static void sendToClients(String msg,SocketAddress fromAddress) throws IOException{
		DatagramSocket socket=new DatagramSocket();
		if(!msg.equals("getIp")){
			byte[] bytes=msg.getBytes();
			for(InetSocketAddress clientAddress:clientAddressList){//遍歷客戶端，然後轉發消息
				System.out.println(clientAddress);
				DatagramPacket packet=new DatagramPacket(bytes, 0,bytes.length,clientAddress);
				//可以進行判斷是否是發送者，若是，可以跳過轉發，根據ip地址判斷
				socket.send(packet);
			}
		}
		socket.close();
	}
}

客戶端

public class Client {  
  
    private static final int BUFFER_SIZE = 1024;  
    private static final String SERVER_IP = "192.168.11.157"; 
    private static final int SERVER_PORT = 1234;	
   
  
    public static void main(String[] args) throws IOException {  
    	SocketAddress server = new InetSocketAddress(SERVER_IP, SERVER_PORT);		
		DatagramSocket ds= new DatagramSocket();		
		String str="getIp";		
		byte buff[]=str.getBytes();		
		byte buffer[]=new byte[8*1024];		
		DatagramPacket dp=new DatagramPacket(buff,0,buff.length,server);				
		Scanner sc=new Scanner(System.in); 		
		ds.send(dp);//發送信息到服務器		
		dp.setData(buffer,0,8*1024);		
		ds.receive(dp);		
		String message=new String(dp.getData(),0,dp.getLength());		
		System.out.println("本機端口和IP信息:"+message);	
		int clientListenPort=Integer.valueOf(message.split(":")[1]);
		System.out.println(clientListenPort);
        new Thread(new ReceiveMsgThread(ds)).start();  
  
        try {  
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
            while(true) {  
                String msg = br.readLine();  
                if ("shutdown".equals(msg)) {  
                    System.out.println("客戶端已退出！");  
                    System.exit(-1);  
                }  
                sendToServer(msg);  
            }  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
    }  
    
    /** 
     * 客戶端向服務端發送消息 
     * @param msg 
     * @throws IOException 
     */  
    private static void sendToServer(String msg) throws IOException {  
    	SocketAddress server = new InetSocketAddress(SERVER_IP, SERVER_PORT);
        DatagramSocket ds = new DatagramSocket();  
        byte[] bytes = msg.getBytes();  
        ds.send(new DatagramPacket(bytes, bytes.length, new InetSocketAddress(SERVER_IP, UDPServer.SERVER_PORT)));  
        ds.close();  
    }  
  
    /** 
     * 用來監聽服務器端發送的信息 
     */  
    private static class ReceiveMsgThread implements Runnable {  
    	DatagramSocket ds=null;
    	DatagramPacket dp=null;
    	String message="";
        private ReceiveMsgThread(DatagramSocket ds) {  
            this.ds = ds;  
        }  
  
        @Override  
        public void run() {  
            //System.out.println("客戶端已經啓動，監聽端口："+clientListenPort);  
            try {  
            	byte buffer[]=new byte[1024];			
    			dp=new DatagramPacket(buffer,0,buffer.length);			
    			byte buff[]=new byte[1024];	
                while (true) {  
                	dp.setData(buff,0,1024);				
    				System.out.println("準備接收");				
    				ds.receive(dp);				
    				message=new String(dp.getData(),0,dp.getLength());	
    				System.out.println("接收到:"+message);	  
                }  
            } catch (SocketException e) {  
                e.printStackTrace();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }  
  
}  

如果覺得有幫助，點個讚唄。本人也在學習當中，有很多需要改進的地方，如果有什麼好的建議和意見，可以指導下我，謝謝！