Java:将数据从服务器发送到监听套接字的所有客户端

Question

我在 java swing 中创建了一个 quizServer 应用程序，它通过套接字连接到多个客户端。我能够通过套接字连接同时从每个客户端向服务器发送数据，但是当我尝试从服务器向客户端发送数据时，只有 1 个客户端接收到该数据。如何修改代码以将数据同时发送到监听套接字的所有客户端？任何代码/伪代码将不胜感激。

这是我的 NetworkClient 类:

public class NetworkClient {

    PrintWriter os = null;
    Socket s1 = null;
    String line = null;
    BufferedReader br = null;
    BufferedReader is = null;
    InetAddress address = null;

    void initClient() {
        try {
            address = InetAddress.getLocalHost();
            System.out.println(address);
        } catch (UnknownHostException ex) {
            Logger.getLogger(NetworkClient.class.getName()).log(Level.SEVERE, null, ex);
        }

        try {
            s1 = new Socket(address, 8888); // You can use static final constant PORT_NUM
            br = new BufferedReader(new InputStreamReader(System.in));
            is = new BufferedReader(new InputStreamReader(s1.getInputStream()));
            os = new PrintWriter(s1.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
            System.err.print("IO Exception");

        }
    }

    void sendVal(int data) {
        os.println(data);
        os.flush();
    }

    void close() {
        try {
            is.close();
            os.close();
            br.close();
            s1.close();
        } catch (Exception ex) {
            Logger.getLogger(NetworkClient.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

这是我的服务器类:

    public class QuizServer {

    QuizJFrame frame;
    ServerThread st;

    void initServer(QuizJFrame frm) {

        frame = frm;
        Socket s = null;
        ServerSocket ss2 = null;
        System.out.println("Server Listening......");
        try {
            ss2 = new ServerSocket(8888); // port number used as 8888

        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("Server error");
        }

        while (true) {
            try {
                s = ss2.accept();
                System.out.println("connection Established");
                st = new ServerThread(s, frm);
                st.start();

            } catch (Exception e) {
                e.printStackTrace();
                System.out.println("Connection Error");

            }
        }
    }
}

这是服务器线程类:

    class ServerThread extends Thread {

    BufferedReader is = null;
    PrintWriter os = null;
    Socket s = null;
    QuizJFrame frame;
    String question[] = {"", "QUESTION 1", "QUESTION 2", "QUESTION 3", "QUESTION 4", "END"};
    int answer[] = {0, 1, 2, 3, 4};
    int index;

    public ServerThread(Socket s, QuizJFrame frm) {
        this.s = s;
        frame = frm;
        index = 1;
        frame.setQuestion(question[index]);
    }

    @Override
    public void run() {
        int option = 0;
        try {
            is = new BufferedReader(new InputStreamReader(s.getInputStream()));
            os = new PrintWriter(s.getOutputStream());

        } catch (IOException e) {
            System.out.println("IO error in server thread:" + e);
        }
        try {
            while (option > -1) {
                try {
                    option = Integer.parseInt(is.readLine());
                    os.println(answer[index] == option);
                    os.flush();
                } catch (NumberFormatException e) { //to handle null value
                }
                System.out.println(result(option));
                frame.output(result(option));
            }
        } catch (IOException ex) {
            Logger.getLogger(ServerThread.class.getName()).log(Level.SEVERE, null, ex);
        }

    }

    String result(int op) {
        if (op == -1) {
            return "Client exited";
        }
        if (answer[index] == op) {
            return "Option " + op + " is the correct answer.";
        } else {
            return "Option " + op + " is incorrect.";
        }
    }

    void nextQues() {
        index++;
        frame.setQuestion(question[index]);
        os.println(-2);
        os.flush();
    }
}

编辑:使用 List<ServerThread>解决了问题。

Answer 1

你的服务器只有一个ServerThread变量，因此只能将数据发送到最后一个添加的一个套接字。相反，考虑给类(class)一个 List<ServerThread>变量以允许它与所有客户端通信。然后在创建连接的 while 循环中，将每个新创建的 ServerThread 添加到此列表中。

您还需要修复服务器的线程问题，以便while (true)循环不会阻塞关键代码。

您还需要升级 ServerThread 类，以便主服务器对象可以与其流进行通信。

此外，您几乎永远不想让一个类扩展 Thread。让它实现 Runnable 来代替。