如果我一次打开两个客户端，Java 客户端会挂起

分类：编程问答

如何解决如果我一次打开两个客户端，Java 客户端会挂起

我正在尝试构建一个类似聊天的东西，这个想法是每当有人打字时，它都会在每个连接的客户端上发送和打印。

如果我只打开服务器和一个客户端，一切都会顺利进行 -- 每当我从客户端发送一些东西时，它都会转到服务器，然后返回并在客户端上打印。

问题是：当我打开第二个客户端时，只有之后发送的第一条消息会打印（在第二个客户端上），然后挂起。它没有错误消息或崩溃，它只是挂起，好像卡在一个什么都不做的无限循环中。与此同时，第一个客户按预期工作。

客户：

package main;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Client extends javax.swing.JFrame 
{
    private Socket client;

    public Client() throws IOException
    {
        initComponents();
        initClient();
        Chat();
    }

    private void initClient()
    {
        try 
        {
            client = new Socket("127.0.0.1",25565);
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE,null,ex);
        }
    }
    
    private void Chat()
    {
        new Thread() 
        {
            @Override
            public void run() 
            {      
                while (true)
                {      
                    try 
                    {     
                        DataInputStream msg = new DataInputStream(client.getInputStream());
                        
                        if (chat.getText().equals("")) chat.setText(msg.readUTF());
                        else chat.setText(chat.getText() + "\n" + msg.readUTF());         
                    } 
                    catch (IOException ex) 
                    {
                        Logger.getLogger(Client.class.getName()).log(Level.SEVERE,ex);
                    }
                }
            }
        }.start();
    }
    
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {

        jScrollPane2 = new javax.swing.JScrollPane();
        msgArea= new javax.swing.JTextArea();
        sendMsgButton = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        chat = new javax.swing.JTextArea();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        msgArea.setColumns(20);
        msgArea.setRows(10);
        jScrollPane2.setViewportView(msgArea);

        sendMsgButton.setText("Send message");
        sendMsgButton.setBorder(javax.swing.BorderFactory.createEmptyBorder(1,1,1));
        sendMsgButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                sendMsgButtonActionPerformed(evt);
            }
        });

        chat.setColumns(20);
        chat.setRows(5);
        chat.setToolTipText("");
        chat.setBorder(javax.swing.BorderFactory.createTitledBorder(javax.swing.BorderFactory.createCompoundBorder(),"Conversas:",javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION,javax.swing.border.TitledBorder.ABOVE_TOP));
        chat.setCursor(new java.awt.Cursor(java.awt.Cursor.TEXT_CURSOR));
        jScrollPane1.setViewportView(chat);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING,layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jScrollPane1)
                    .addComponent(jScrollPane2))
                .addContainerGap())
            .addGroup(layout.createSequentialGroup()
                .addGap(142,142,142)
                .addComponent(sendMsgButton,javax.swing.GroupLayout.PREFERRED_SIZE,121,javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(147,Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1,312,javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18,18,18)
                .addComponent(jScrollPane2,86,18)
                .addComponent(sendMsgButton,25,18))
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void sendMsgButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_sendMsgButtonActionPerformed
        try 
        {
            PrintStream out = new PrintStream(client.getOutputStream());
            out.println("User: " + msgArea.getText());
            msgArea.setText("");
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(Client.class.getName()).log(Level.SEVERE,ex);
        }
    }//GEN-LAST:event_sendMsgButtonActionPerformed

    public static void main(String args[])
    {
        try 
        {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) 
            {
                if ("Nimbus".equals(info.getName())) 
                {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } 
        catch (ClassNotFoundException ex) 
        {
            java.util.logging.Logger.getLogger(Client.class.getName()).log(java.util.logging.Level.SEVERE,ex);
        } 
        catch (InstantiationException ex) 
        {
            java.util.logging.Logger.getLogger(Client.class.getName()).log(java.util.logging.Level.SEVERE,ex);
        } 
        catch (IllegalAccessException ex) 
        {
            java.util.logging.Logger.getLogger(Client.class.getName()).log(java.util.logging.Level.SEVERE,ex);
        } 
        catch (javax.swing.UnsupportedLookAndFeelException ex) 
        {
            java.util.logging.Logger.getLogger(Client.class.getName()).log(java.util.logging.Level.SEVERE,ex);
        }

        java.awt.EventQueue.invokeLater(() -> {
            try {
                new Client().setVisible(true);
            } catch (IOException ex) {
                Logger.getLogger(Client.class.getName()).log(Level.SEVERE,ex);
            }
        });        
    }

    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JTextArea msgArea;
    private javax.swing.JButton sendMsgButton;
    private javax.swing.JTextArea chat;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    // End of variables declaration//GEN-END:variables
}

服务器：

package main;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList; 
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Server
{     
    private static ArrayList<ClientHandler> clients = new ArrayList<>();
    private static ExecutorService pool = Executors.newFixedThreadPool(5);
    
    public static void main(String args[])
    {  
        int door = 25565;
        
        try 
        {
            ServerSocket server = new ServerSocket(porta,InetAddress.getByName("127.0.0.1"));
            System.out.println("Server running on " + server.getInetAddress().getHostAddress() + ":" + door);

            while (true)
            {
                Socket client = server.accept();
                System.out.println("Client conectado do IP " + client.getInetAddress().getHostAddress());
                ClientHandler clientThread = new ClientHandler(client,clients);
                clients.add(clientThread);

                pool.execute(clientThread);
            }        
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE,ex);
        }
    }   
}

ClientHandler：（由服务器使用）

package main;

import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ClientHandler implements Runnable
{
    private Socket client;
    private Scanner in ;
    private DataOutputStream out;
    private ArrayList<ClientHandler> clients;
    
    public ClientHandler(Socket clientSocket,ArrayList<ClientHandler> clients) throws IOException
    {
        this.client = clientSocket;
        this.clients = clients;
        in = new Scanner(cliente.getInputStream());
        out = new DataOutputStream(cliente.getOutputStream());
    }
    
    private void sendToAll(String message) throws IOException
    {
        for (ClientHandler Client : clients)
        {
            Client.out.writeUTF(message);
        }
    }
    
    @Override
    public void run() 
    {
        while(in.hasNextLine())
        {
            try 
            {
                String msg = in.nextLine();
                System.out.println(msg);
                sendToAll(msg);
            } 
            catch (IOException ex) 
            {
                Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE,ex);
            }
        }

        try 
        {
            out.close();
            in.close();
        } 
        catch (IOException ex) 
        {
            Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE,ex);
        }
    }
}

解决方法

回答我自己的问题：问题在于使用 JTextArea，它与长字符串或其他东西有一些奇怪的交互。

我把它换成了 JTextPane，现在一切正常。

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