java - 查找导致 java.net.SocketException : Unrecognized Windows Sockets error: 0: Cannot bind 的隐藏错误

Question

**这里是两个点之间聊天的简单代码。根据我的说法，代码做了它应该做的，但我在解决这个 SocketException 错误时遇到了困难。在我进行最后修改之前，这段代码工作正常。现在我发现很难追踪错误。

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.util.*;
import java.net.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class UDPchat extends Thread implements ActionListener
{
    JFrame f;
    JPanel p;
    JTextField text;
    JButton b;
    JTextArea ta;
    private final static String newline = "\n";
    private final static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

    int porttor=7777; // port to send/receive datagrams on
    //int porttos=5555;
    String remoteIPaddress= ("127.0.0.1");      // IP to send datagrams

    public UDPchat() throws Exception
    {
        start();      // start thread to receive and display datagrams
        f=new JFrame("CHAT WINDOW");
        p= new JPanel();
        text = new JTextField();
        text.setColumns(25);

        b = new JButton("SEND");

        b.addActionListener(this);

        ta = new JTextArea("Chat messages",20,50);

        ta.setEditable(false);

        f.setLayout(new FlowLayout());

        p.add(text,BorderLayout.NORTH);

        p.add(b,BorderLayout.SOUTH);

        f.setLayout(new BorderLayout());

        f.add(ta,BorderLayout.NORTH);

        f.add(p,BorderLayout.SOUTH);

        f.setSize(400, 400);

        f.setVisible(true);
    }

    @Override

    public void actionPerformed(ActionEvent e)
    {

        try
        {

            String s = text.getText();  // read a String

            text.setText(" ");

            ta.append(newline);

            ta.append(s);

            //System.out.println("Sending to " + remoteIPaddress + " socket " + port + " data: " + s);

            byte[] data = s.getBytes();  // convert to byte array

            DatagramSocket theSocket = new DatagramSocket();  // create datagram socket and the datagram

            DatagramPacket   theOutput = new DatagramPacket(data, data.length, InetAddress.getLocalHost(), 5555);

            theSocket.send(theOutput);     

        }

        catch(Exception et)
        {

            System.out.println("Error sending datagram" + et);

        }

    }

    // thread run method, receives datagram and display contents as a string
    public void run()                
    {

        try
        {

            // open DatagramSocket to receive 

            DatagramSocket ds = new DatagramSocket(7777);

            // loop forever reading datagrams from the DatagramSocket

            while (true)
            {

                byte[] buffer = new byte[65507];  // array to put datagrams in

                DatagramPacket dp = new DatagramPacket(buffer, buffer.length);  // DatagramPacket to hold the datagram

                try {

                    ds.receive(dp);

                } catch (IOException e) {

                    // TODO Auto-generated catch block

                    System.err.println("chat error2 " + e);

                }   // wait for next datagram

                String s = new String(dp.getData(),0,dp.getLength()); // get contents as a String

                System.out.println("UDP datagram length " + s.length()+ "  from IP " + dp.getAddress() + " received: " + s );

                ta.append(newline);

                ta.append(s);

            }

        }

        catch (SocketException se)
        {

             System.err.println("chat error1 " + se);

        }

        //catch (IOException se) {System.err.println("chat error2 " + se);}

        //System.exit(1);   // exit on error

    }

    public static void main(String args[]) throws Exception
    {

        UDPchat c=new UDPchat();

    }

}

Answer 1

检查你在代码中制作了两种类型的 DatagramSockets，尝试提供相同的 7777 端口。一个在你的 actionPerformed() 方法中:

DatagramSocket theSocket = new DatagramSocket();  // create datagram socket and the datagram

和你的运行方法中的那个:

// open DatagramSocket to receive 

DatagramSocket ds = new DatagramSocket(7777);

Upper 构造函数正在创建一个数据报套接字并将其绑定(bind)到本地主机上的任何可用端口，第二个正在尝试到达端口 7777。尝试使用相同的端口号初始化两者，这将解决问题你。

希望这能以某种方式提供帮助。

问候