Java: 使用 AWT 按钮断开与聊天服务器的连接

Question

我正在编写一个简单的多线程 client/server 聊天系统。项目要求指定：“连接仅在单击连接按钮时发生。断开连接按钮应断开连接。用户应该能够随意连接、断开连接、重新连接。”基本上，我连接了连接按钮和运行。但是，当我尝试断开连接时，我陷入了无限循环，客户端（在命令行上）无限打印“Sock closed”，而服务器端无限打印“Message read：null”。这让我查看了我所有的 for(;;) 循环以某种方式关闭它们内的连接，但是我无法弄清楚如何关闭这些循环内的连接。请帮忙，这是我的第一个套接字编程项目，我对这个项目感到非常难过！谢谢大家

客户：

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.ArrayList;

public class ClientFrame extends Frame{
    public ClientFrame(){
        setSize(500,500);
        setTitle("Chat Client");
        addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent We){
                System.exit(0);
            }
        });
        add(new ClientPanel(), BorderLayout.CENTER);        
        setVisible(true);
    }
    public static void main(String[] args){
        new ClientFrame();
    }

} // end ClientFrame

class ClientPanel extends Panel implements ActionListener, Runnable{
    TextField tf;
    TextArea ta;
    List list;
    Button connect, disconnect;
    Socket socketToServer;
    PrintWriter pw;
    BufferedReader br;
    Thread t;
    String userName;

    public ClientPanel(){
        setLayout(new BorderLayout());
        tf = new TextField();
        ta = new TextArea();
        list = new List();
        connect = new Button("Connect");
        disconnect = new Button("Disconnect");
        Panel bPanel = new Panel();
        bPanel.add(connect);
        disconnect.setEnabled(false);
        bPanel.add(disconnect);
        
        tf.addActionListener(this);
        add(tf, BorderLayout.NORTH);
        add(ta, BorderLayout.CENTER);
        add(list, BorderLayout.EAST);
        add(bPanel, BorderLayout.SOUTH);
        
        connect.addActionListener(this);
        disconnect.addActionListener(this);
    
    } // end ClientPanel constructor


    public void actionPerformed(ActionEvent ae){
        if (ae.getSource() == tf){
            String temp = tf.getText();
            pw.println(userName+": "+temp);
            tf.setText("");
        } else if (ae.getSource() == connect){
            if(tf.getText() == null || tf.getText().equals("")){
                    ta.append("Must enter a name to connect\n");
                }else { 
                    userName = tf.getText();
                    connect.setEnabled(false);
                    disconnect.setEnabled(true);
                    tf.setText("");     
                    try{
                        socketToServer = new Socket("127.0.0.1", 3000);
                        pw = new PrintWriter(new OutputStreamWriter
                                (socketToServer.getOutputStream()), true);
                        br = new BufferedReader(new InputStreamReader
                                (socketToServer.getInputStream()));
                    }catch(UnknownHostException uhe){
                        System.out.println(uhe.getMessage());
                    }catch(IOException ioe){
                        System.out.println(ioe.getMessage());
                    } 
                }

                    t = new Thread(this);
                    t.start();
                    pw.println(userName);
                    pw.println(userName +" has entered the chat.");
        }else if (ae.getSource()== disconnect){
            try{
                t.interrupt();
                socketToServer.close();
            }catch(IOException ioe){
                System.out.println(ioe.getMessage());
            }
        }
    } // end actionPerformed

    public void run(){
            for(;;){
                try{
                    String temp = br.readLine();
                    ta.append(temp + "\n");
                }catch(IOException ioe){
                    System.out.println(ioe.getMessage());
                } 
            }
    } // end run

} // end ClientPanel

服务器：

import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.awt.*;

public class ThreadedServerWithPresence{  
    public static void main(String[] args){  
        ArrayList<ThreadedHandlerWithPresence> handlers;
            try{    
            handlers = new ArrayList<ThreadedHandlerWithPresence>();
            ServerSocket s = new ServerSocket(3000);
                for(;;){  
                Socket incoming = s.accept( );
                new ThreadedHandlerWithPresence(incoming, 
                                    handlers).start();

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

class ThreadedHandlerWithPresence extends Thread{  

    Socket incoming;
    ArrayList<ThreadedHandlerWithPresence> handlers;
    PrintWriter pw;
    BufferedReader br;
    String userName;

    public ThreadedHandlerWithPresence(Socket i,
        ArrayList<ThreadedHandlerWithPresence> handlers){ 
        incoming = i;
        this.handlers = handlers;
        handlers.add(this);
    }

    public void setUserName(String userName){
        this.userName = userName;
    }

    public String getUserName(){
        return userName;
    }
   
    public void run(){  
        try{    
            br = new BufferedReader(new InputStreamReader
                            (incoming.getInputStream()));

            pw = new PrintWriter(new OutputStreamWriter
                            (incoming.getOutputStream()),true);
           
            String firstLine = br.readLine();
            setUserName(firstLine);

            for(;;){
                
                String temp = br.readLine();

                System.out.println("Message read: " + temp);
        
                for(int i = 0; i < handlers.size(); i++){
                    handlers.get(i).pw.println(temp);
                }
            }           
            }catch (Exception e){  
            System.out.println(e);
            }finally{
                handlers.remove(this); 
            } 
    }
}

Answer 1

客户端

您的运行方法不处理中断，因此 for 循环不会结束，它会继续尝试接收消息。

你必须添加一个可以被中断和抛出的动作 InterruptedException，Thread.sleep 在这种情况下是一个很好的选择，同时减少了 CPU 的使用（你不需要每时每刻检查新消息）。

    try {
        for (; ; ) {
            try {
                String temp = br.readLine();
                ta.append(temp + "\n");

            } catch (IOException ioe) {
                System.out.println(ioe.getMessage());

            }
            Thread.sleep(10);
        }
    } catch (InterruptedException e) {
        System.out.println("Disconnected.");
    }

服务器

当br.readLine() returns null时，表示连接已被客户端关闭，您应该停止接收消息。

        String temp = br.readLine();

        if(temp == null)
            break;

Java: 使用 AWT 按钮断开与聊天服务器的连接

Java: Using AWT button to disconnect from chat server

java

multithreading

client-server

awt

java-threads