java - 向所有客户端发送消息(客户端 - 服务器通信)

Question

所以现在，我正在制作一个基于多线程的客户端服务器应用程序。在服务器端，我为接受的每个连接创建一个线程。

在线程类中，我创建了一个向客户端发送命令的方法。我只想要的是，如何向所有正在运行的客户端发送参数？对于简单的声明，我只是想让这个服务器向所有连接的客户端发送消息。

我已经读过this post并从 this link 中找到 sendToAll(String message) 方法.但是当我在我的代码中尝试时， ServerSocket 中没有这样的方法。

好的，这是我的服务器和线程示例代码。

class ServerOne{

ServerSocket server = null;
...

ServerOne(int port){
            System.out.println("Starting server on port "+port);
    try{
      server = new ServerSocket(port);
              System.out.println("Server started successfully and now waiting for client");

    } catch (IOException e) {
      System.out.println("Could not listen on port "+port);
      System.exit(-1);
    }
}

public void listenSocket(){ 
    while(true){
        ClientWorker w;
        try{
            w = new ClientWorker(server.accept());
            Thread t = new Thread(w);
            t.start();
        } catch (IOException e) {
            System.out.println("Accept failed: 4444");
            System.exit(-1);
        }   
    }
}

protected void finalize(){
    try{
        server.close();
    } catch (IOException e) {
        System.out.println("Could not close socket");
        System.exit(-1);
    }
}
}

class ClientWorker implements Runnable{
Socket client;

ClientWorker(Socket client){
    this.client = client;
}
public void run(){
    ...
      sendCommand(parameter);
    ...
}

public void sendCommand(String command){
    PrintWriter out = null;
    try {
        out = new PrintWriter(client.getOutputStream(), true);
        out.println(command);
    } catch (IOException ex) {}
}

}

感谢您的帮助:)

Answer 1

The below answer, is not recommended for a full fledged server, as for this you should use Java EE with servlets, web services etc.

This is only intended where a few computers want to connect to perform a specific task, and using simple Java sockets is not a general problem. Think of distributed computing or multi-player gaming.

编辑:自第一篇文章以来，我已经大大更新了这个架构，现在已经过测试并且是线程安全的。有需要的可以下载here .

只需使用(直接或子类化)Server和Client，start()它们，一切就绪。阅读内联评论以获得更强大的选项。

---

虽然客户端之间的通信相当复杂，但我会尽量简化它。

以下是服务器中的点:

• 保留已连接客户端的列表。
• 定义一个线程，用于服务器输入。
• 定义接收消息的队列。
• 从队列中轮询并使用它的线程。
• 发送消息的一些实用方法。

对于客户:

• 定义一个线程，用于客户端输入。
• 定义接收消息的队列。
• 从队列中轮询并使用它的线程。

这是服务器类:

public class Server {
    private ArrayList<ConnectionToClient> clientList;
    private LinkedBlockingQueue<Object> messages;
    private ServerSocket serverSocket;

    public Server(int port) {
        clientList = new ArrayList<ConnectionToClient>();
        messages = new LinkedBlockingQueue<Object>();
        serverSocket = new ServerSocket(port);

        Thread accept = new Thread() {
            public void run(){
                while(true){
                    try{
                        Socket s = serverSocket.accept();
                        clientList.add(new ConnectionToClient(s));
                    }
                    catch(IOException e){ e.printStackTrace(); }
                }
            }
        };

        accept.setDaemon(true);
        accept.start();

        Thread messageHandling = new Thread() {
            public void run(){
                while(true){
                    try{
                        Object message = messages.take();
                        // Do some handling here...
                        System.out.println("Message Received: " + message);
                    }
                    catch(InterruptedException e){ }
                }
            }
        };

        messageHandling.setDaemon(true);
        messageHandling.start();
    }
    
    private class ConnectionToClient {
        ObjectInputStream in;
        ObjectOutputStream out;
        Socket socket;

        ConnectionToClient(Socket socket) throws IOException {
            this.socket = socket;
            in = new ObjectInputStream(socket.getInputStream());
            out = new ObjectOutputStream(socket.getOutputStream());

            Thread read = new Thread(){
                public void run(){
                    while(true){
                        try{
                            Object obj = in.readObject();
                            messages.put(obj);
                        }
                        catch(IOException e){ e.printStackTrace(); }
                    }
                }
            };

            read.setDaemon(true); // terminate when main ends
            read.start();
        }

        public void write(Object obj) {
            try{
                out.writeObject(obj);
            }
            catch(IOException e){ e.printStackTrace(); }
        }
    }

    public void sendToOne(int index, Object message)throws IndexOutOfBoundsException {
        clientList.get(index).write(message);
    }

    public void sendToAll(Object message){
        for(ConnectionToClient client : clientList)
            client.write(message);
    }

}

---

这里是 Client 类:

public class Client {
    private ConnectionToServer server;
    private LinkedBlockingQueue<Object> messages;
    private Socket socket;

    public Client(String IPAddress, int port) throws IOException{
        socket = new Socket(IPAddress, port);
        messages = new LinkedBlokingQueue<Object>();
        server = new ConnecionToServer(socket);

        Thread messageHandling = new Thread() {
            public void run(){
                while(true){
                    try{
                        Object message = messages.take();
                        // Do some handling here...
                        System.out.println("Message Received: " + message);
                    }
                    catch(InterruptedException e){ }
                }
            }
        };

        messageHandling.setDaemon(true);
        messageHandling.start();
    }

    private class ConnectionToServer {
        ObjectInputStream in;
        ObjectOutputStream out;
        Socket socket;

        ConnectionToServer(Socket socket) throws IOException {
            this.socket = socket;
            in = new ObjectInputStream(socket.getInputStream());
            out = new ObjectOutputStream(socket.getOutputStream());

            Thread read = new Thread(){
                public void run(){
                    while(true){
                        try{
                            Object obj = in.readObject();
                            messages.put(obj);
                        }
                        catch(IOException e){ e.printStackTrace(); }
                    }
                }
            };

            read.setDaemon(true);
            read.start();
        }

        private void write(Object obj) {
            try{
                out.writeObject(obj);
            }
            catch(IOException e){ e.printStackTrace(); }
        }


    }

    public void send(Object obj) {
        server.write(obj);
    }
}