java 显示从服务器到所有连接客户端的在线用户

Display online users from server to all connected clients

提问by Shahar Galukman

I'm building simple socket server-client application consisting of: Server project(which creates new client handler thread when socket is accepted) and a Client project(which establishing connection with the server and displaying gui with message thread open).

我正在构建简单的套接字服务器-客户端应用程序，包括： 服务器项目（在接受套接字时创建新的客户端处理程序线程）和客户端项目（与服务器建立连接并在消息线程打开的情况下显示 gui）。

So far I'm able to connect using multiple clients and chat with no problems. I've set a command called !getusersthat should display all connected users to the requesting client. When I do so, I'm suddenly unable to continue and chat, the client simply get stuck, I do get the connected users list though.

到目前为止，我能够使用多个客户端进行连接并毫无问题地聊天。我已经设置了一个名为的命令!getusers，该命令应该向请求客户端显示所有连接的用户。当我这样做时，我突然无法继续聊天，客户端只是卡住了，但我确实获得了连接的用户列表。

As for a request here is the entire client code:

至于这里的请求是整个客户端代码：

import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import static java.lang.System.out;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ChatClient extends JFrame implements ActionListener {
String uname;
PrintWriter pw;
BufferedReader br;
JTextArea taMessages, taUserList;
JTextField tfInput;
JButton btnSend, btnExit;
Socket client;

public ChatClient(String uname, String servername) throws Exception {
    super("Connected as: " + uname);  // set title for frame
    this.uname = uname;
    client = new Socket(servername, 18524);
    br = new BufferedReader(new InputStreamReader(client.getInputStream()));
    pw = new PrintWriter(client.getOutputStream(), true);
    pw.println(uname);  // send name to server
    //bring up the chat interface
    buildInterface();
    new MessagesThread().start();  // create thread that listens for messages
}

public void buildInterface() {
    btnSend = new JButton("Send");
    btnExit = new JButton("Exit");
    //chat area
    taMessages = new JTextArea();
    taMessages.setRows(10);
    taMessages.setColumns(50);
    taMessages.setEditable(false);
    //online users list
    taUserList = new JTextArea();
    taUserList.setRows(10);
    taUserList.setColumns(10);
    taUserList.setEditable(false);
    //top panel (chat area and online users list
    JScrollPane chatPanel = new JScrollPane(taMessages, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
            JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
    JScrollPane onlineUsersPanel = new JScrollPane(taUserList, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
            JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
    JPanel tp = new JPanel(new FlowLayout());
    tp.add(chatPanel);
    tp.add(onlineUsersPanel);
    add(tp, "Center");
    //user input field
    tfInput = new JTextField(50);
    //buttom panel (input field, send and exit)
    JPanel bp = new JPanel(new FlowLayout());
    bp.add(tfInput);
    bp.add(btnSend);
    bp.add(btnExit);
    add(bp, "South");
    btnSend.addActionListener(this);
    tfInput.addActionListener(this);//allow user to press Enter key in order to send message
    btnExit.addActionListener(this);
    setSize(500, 300);
    setVisible(true);
    pack();
}

@Override
public void actionPerformed(ActionEvent evt) {
    if (evt.getSource() == btnExit) {
        pw.println("!end");  // send end to server so that server know about the termination
        System.exit(0);
    } else if(tfInput.getText().contains("!getusers")){
            pw.println("!getusers");
    }else{
        // send message to server
        pw.println(tfInput.getText());
    }
}

public static void main(String args[]) {

    // take username from user
    String name = JOptionPane.showInputDialog(null, "Enter your name: ", "Username",
            JOptionPane.PLAIN_MESSAGE);
    String servername = "localhost";
    try {
        new ChatClient(name, servername);
    } catch (Exception ex) {
        out.println("Unable to connect to server.\nError: " + ex.getMessage());
    }

} // end of main

// inner class for Messages Thread
class MessagesThread extends Thread {

    @Override
    public void run() {
        String line;
        try {
            while (true) {
                line = br.readLine();
                taMessages.append(line + "\n");
                taMessages.setCaretPosition(taMessages.getDocument().getLength());//auto scroll to last message
            } // end of while
        } catch (Exception ex) {
        }
    }
    }
} //  end of client

Which then accepted and handled by the server, following is the entire server code:

然后由服务器接受并处理，以下是整个服务器代码：

public class ChatServer {

    Vector<String> users = new Vector<String>();
    Vector<HandleClient> clients = new Vector<HandleClient>();

    public void process() throws Exception {
        ServerSocket server = new ServerSocket(18524);
        out.println("Server Started...");
        while (true) {
            Socket client = server.accept();
            //add incoming client to connected clients vector.
            HandleClient c = new HandleClient(client);
            clients.add(c);
        }  // end of while
    }

    public static void main(String... args) throws Exception {
        new ChatServer().process();
    } // end of main

    public void broadcast(String user, String message) {
        // send message to all connected users
        for (HandleClient c : clients) {
            c.sendMessage(user, message);
        }
    }

    /*
     * Inner class, responsible of handling incoming clients.
     * Each connected client will set as it's own thread.
     */
    class HandleClient extends Thread {

        String name = "";//client name/username
        BufferedReader input;//get input from client
        PrintWriter output;//send output to client

        public HandleClient(Socket client) throws Exception {
            // get input and output streams
            input = new BufferedReader(new InputStreamReader(client.getInputStream()));
            output = new PrintWriter(client.getOutputStream(), true);
            // read name
            name = input.readLine();
            users.add(name); // add to users vector
            broadcast(name, " Has connected!");
            start();
        }

        public void sendMessage(String uname, String msg) {
            output.println(uname + ": " + msg);
        }

        public void getOnlineUsers() {
            for (HandleClient c : clients) {
                for (int i = 0; i < users.size(); i++) {
                    broadcast("", users.get(i));
                }
            }
        }

        public String getUserName() {
            return name;
        }

        public void run() {
            String line;
            try {
                while (true) {
                    line = input.readLine();
                    if (line.equals("!end")) {
                        //notify all for user disconnection
                        broadcast(name, " Has disconnected!");
                        clients.remove(this);
                        users.remove(name);
                        break;
                    } else if(line.equals("!getusers")){
                        getOnlineUsers();
                        break;
                    }
                    broadcast(name, line); // method  of outer class - send messages to all
                } // end of while
            } // try
            catch (Exception ex) {
                System.out.println(ex.getMessage());
            }
        } // end of run()
    } // end of inner class
} // end of Server

Should I defince a new PrintWriter object for handling the onlineUsers request? I'm sure I'm missing something here, but yet to figure out what exactly.

我应该定义一个新的 PrintWriter 对象来处理 onlineUsers 请求吗？我确定我在这里遗漏了一些东西，但还没有弄清楚到底是什么。

回答by TheMerovingian

Ah, I have solved the puzzle.

啊，我已经解决了这个难题。

public void run() {
        String line;
        try {
            while (true) {
                line = input.readLine();
                if (line.equals("!end")) {
                     // Blah
                } else if(line.equals("!getusers")){
                    getOnlineUsers();
                    break;    << This breaks your read loop
                }
                broadcast(name, line); // method  of outer class - send messages to all
            } // end of while
        } // try
        catch (Exception ex) {
            System.out.println(ex.getMessage());
        }
    } // end of run()

The breakstatement in your run()loop terminates your reading loop, so the server is no longer "listening" to your client. I believe if you remove the break, it should be all good.

循环中的break语句会run()终止您的阅读循环，因此服务器不再“听”您的客户端。我相信如果你删除break，它应该一切都很好。