客户端和服务端问题

Question

服务器端代码：
import java.io.*;
import java.net.*;public class ChatServer { public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(7777);
while(true) {
Socket s = ss.accept();
System.out.println("a client connected!");
DataInputStream dis = new DataInputStream(s.getInputStream());
//String s1 = "";
//while( (s1 = dis.readLine())!= null)
//{
// System.out.println(s1);
//}
String str = dis.readUTF();
System.out.println(str);
dis.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}}客户端代码：
import java.awt.*;
import java.io.*;
import java.net.*;
import java.awt.event.*;public class ChatClient extends Frame { TextField tfTxt = new TextField();
TextArea taContent = new TextArea();
Socket s = null; public static void main(String[] args) {
new ChatClient().launchFrame();
} public void launchFrame() {
this.setLocation(400, 300);
this.setSize(300, 300);
add(tfTxt, BorderLayout.SOUTH);
add(taContent, BorderLayout.NORTH);
pack();
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
tfTxt.addActionListener(new TFListener());
setVisible(true);
connect();
}

private void connect() {
try {
Socket s = new  Socket("127.0.0.1",7777);
System.out.println("connected!");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

private class TFListener implements ActionListener { public void actionPerformed(ActionEvent e) {
String str = tfTxt.getText().trim();
//String s2 = taContent.getText();
taContent.setText(str);
tfTxt.setText("");
try {
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
dos.writeUTF(str);
dos.flush();
dos.close();
} catch (IOException e1) {
e1.printStackTrace();
}

}

}

}运行客户端的时候，一往TextField里面输入数据发送的时候就出现了如下错误：
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.DataInputStream.readUnsignedShort(Unknown Source)
at java.io.DataInputStream.readUTF(Unknown Source)
at java.io.DataInputStream.readUTF(Unknown Source)
at ChatServer.main(ChatServer.java:18)
请问是什么原因呢？该如何去修改呢？

Answer 1

ChatServer
import java.io.*;
import java.net.*;
import java.util.logging.Level;
import java.util.logging.Logger;public class ChatServer {    public static void main(String[] args) {
        try {
            ServerSocket ss = new ServerSocket(7777);
            while (true) {
                Socket s = ss.accept();
                System.out.println("a new client connected!");
                final DataInputStream dis = new DataInputStream(s.getInputStream());
                new Thread(new Runnable() {//多线程,支持多个客户端
                    public void run() {
                        String s1 = "";
                        try {
                            while ((s1 = dis.readUTF()) != null) {
                                System.out.println(s1);
                                ////
                                ////
                            }
                        } catch (IOException ex) {
                            Logger.getLogger(ChatServer.class.getName()).log(Level.SEVERE, null, ex);
                            System.out.println("断开连接");
                        }
                    }
                }).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}ChatClient
import java.awt.*;
import java.io.*;
import java.net.*;
import java.awt.event.*;public class ChatClient extends Frame {    TextField tfTxt = new TextField();
    TextArea taContent = new TextArea();
    Socket s = null;    public static void main(String[] args) {
        new ChatClient().launchFrame();
    }    public void launchFrame() {
        this.setLocation(400, 300);
        this.setSize(300, 300);
        add(tfTxt, BorderLayout.SOUTH);
        add(taContent, BorderLayout.NORTH);
        pack();
        this.addWindowListener(new WindowAdapter() {            @Override
            public void windowClosing(WindowEvent e) {
                try {
                    if(s!=null)
                        s.close();
                } catch (IOException ex) {
                }
                System.exit(0);
            }
        });
        tfTxt.addActionListener(new TFListener());
        setVisible(true);
        connect();
    }    private void connect() {
        try {
            /*Socket  这里的问题*/ s = new Socket("127.0.0.1", 7777);
            System.out.println("connected!");
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }    private class TFListener implements ActionListener {        public void actionPerformed(ActionEvent e) {
            String str = tfTxt.getText().trim();
//String s2 = taContent.getText();
            taContent.setText(str);
            tfTxt.setText("");
            try {
                DataOutputStream dos = new DataOutputStream(s.getOutputStream());
                dos.writeUTF(str);
                dos.flush();
                //dos.close();//////////////////////
            } catch (IOException e1) {
                e1.printStackTrace();
            }        }
    }
}

Answer 2

我已经知道错在哪了，已经定义了成员变量Socket，在Socket s = new Socket("127.0.0.1")中就不该在重新定义个Socket局部变量了，出现了空指针异常错误。