Java客户端服务器多线程，仅适用于一个连接

Question

I did my client-server application but at the moment only one user can use it. Could you help me how to make it working for more than one user. I have the following functionality: On every two minutes counter is starting to decrease. Every user have 30 seconds to connect to the application. Every connected user should see same result with which he should make some other actions. I made it by this way at the moment. The code in the different cases is not so important. I need an advice how to make it working as a structure of the code. Thanks in advance!

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

public class MultiServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;

        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 4444.");
            System.exit(-1);
        }

        while (listening)
        new MultiServerThread(serverSocket.accept()).start();

        serverSocket.close();
    }
}




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

public class MultiServerThread extends Thread {
    private Socket socket = null;

    public MultiServerThread(Socket socket) {
        super("MultiServerThread");
    this.socket = socket;
    }

    public void run() {
        try {

            ObjectOutputStream toServer = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream fromServer = new ObjectInputStream(socket.getInputStream());

            int userProcess = 0;
            Object data = 11111;
            boolean listening = true;


            CountDown c = new CountDown();
            int timeRemaining = 900;

            while (listening) {
                boolean send = true;
                Object ob;
                try {
                    ob = fromServer.readObject();
                    userProcess = Integer.parseInt(ob.toString());
                    HashMap<String,Integer> finalScores = new HashMap<String,Integer>();
                    if(userProcess == 0) {
                        timeRemaining = c.getRemainingTime();
                        int temp = 999;
                        while(timeRemaining-110>0) {
                            timeRemaining = c.getRemainingTime();
                            if(temp != timeRemaining) {
                                toServer.writeObject(timeRemaining-110);
                                toServer.flush();
                                temp = timeRemaining;
                            }
                        } 
                    } 
                    if(userProcess == 0 && timeRemaining-110 < 0) {
                        c = new CountDown();
                        send = false;
                    }

                    if(userProcess == 1) {   
                        BoardGeneraor board = new BoardGeneraor();
                        data = board.getBoard();
                    } 
                    if(userProcess == 2) {   
                        int score = (Integer)fromServer.readObject();
                        String username = (String)fromServer.readObject();
                        finalScores.put(username, score);
                        data = finalScores;
                        c = new CountDown();
                    }
                    if(send) {
                       toServer.writeObject(data);
                        toServer.flush();
                    } else {
                        toServer.writeObject("quit");
                        toServer.flush();
                    }
                } catch (ClassNotFoundException e) {
                    System.out.println(e);
                }
            }

            fromServer.close();
            toServer.close();
            socket.close(); 

        } catch(IOException e) {
             System.out.println(e);
        }
    }
}

Answer 1

I think your problem is that you have confused the server and client and have put the client and server code within the same Java file. It looks like you intend MultiServerThread to be the client, since it interprets the socket's output stream as going "to server" and the socket's input stream as coming "from server." But when you create a MultiServerThread with serverSocket.accept() , you're giving it a socket that represents the server's side of the connection to one client. Thus the output stream returned by socket.getOutputStream() represents a stream from the server to the client . What MultiServerThread should actually represent is one instance of the server talking to a client, not one instance of a client connecting to the server.

In order to have clients connect to your server, you'll need a separate Java file, say Client.java, containing a separate class with a separate main method. This class should open a connection to the server with the Socket(String host, int port) constructor, and treat the input stream of that socket as a stream of input from the server. Here's a simple example:

public class Client {

    public static void main(String[] args) {

        Socket serverConnection = null;

        try {
            serverConnection = new Socket("localhost", 4444);
        } catch(IOException e) {
            System.err.println("Could not connect to server");
            System.exit(-1);
        }

        try {
            ObjecttInputStream fromServer = new ObjectInputStream(serverConnection.getInputStream());
            Object ob = fromServer.readObject();
        } catch(IOException e) {
            System.err.println("Error reading from server");
        }

    }

}

Once you've started your server by running the MultiServer.class file, you can start a client by running the Client.class file (in a separate window, while the server is still running).