java中的简单Udp通讯程序

前言

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本人学习java中的socket练手的小程序，高手请飘过，仅作为学习笔记，没有技术含量。

分析

这里使用两个独立线程负责发包和收包，设计两个类实现Runnable接口，利用管道和主窗体通信。

代码

mainfest.txt文件：这里注意有myqq.MyQQ后的回车符和myqq.MyQQ前的空格

Main-Class: myqq.MyQQ

MyQQ.java文件：

package myqq;

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

class UdpSend implements Runnable
{
    private DatagramSocket ds;
    private InputStream is;
    public UdpSend(DatagramSocket ds,InputStream is)
    {
        try
        {
            this.ds = ds;
            this.is = is;
        }
        catch (Exception e)
        {
            throw new RuntimeException("发送端错误");
        }
    }
    public void run()
    {
        try
        {
            //读取来自文本框的数据
            BufferedReader br = new BufferedReader(new InputStreamReader(is));

            String s = null;
            while((s=br.readLine())!=null)
            {
                //当输入886时停止发送数据
                if("886".equals(s))
                    break;

                byte[] buf  = s.getBytes();

                //这里是要发送数据包的目标ip和端口，也可以设置成广播地址
                DatagramPacket dp = new DatagramPacket(buf,buf.length,InetAddress.getByName("169.254.255.255"),12345);
                ds.send(dp);
            }
            br.close();

            ds.close();
        }
        catch (Exception e)
        {
            throw new RuntimeException("发送端错误");
        }

    }
}

class UdpRecv implements Runnable
{
    private DatagramSocket ds;
    private OutputStream is;

    public UdpRecv(DatagramSocket ds,OutputStream is)
    {
        try
        {
            this.ds = ds;
            this.is = is;
        }
        catch (Exception e)
        {
            throw new RuntimeException("接收端错误");
        }
    }

    public void run()
    {
        try
        {
            while(true)
            {
                //Udp最大的数据包长度是64k
                byte[] buf = new byte[1024*64];

                DatagramPacket dp = new DatagramPacket(buf,buf.length);

                ds.receive(dp);

                //获取数据包的源ip和数据内容
                String ip = dp.getAddress().getHostAddress();
                String data = new String(dp.getData(),0,dp.getLength());

                String s = ip+"::"+data;

                is.write(s.getBytes());
                is.flush();
            }
        }
        catch (Exception e)
        {
            throw new RuntimeException("接收端错误");
        }

    }
}

class MyQQ
{
    private static Frame r;
    private static TextArea tsend;//发送文本框
    private static TextArea trecv;//接收文本框

    //发送通信管道
    private static PipedInputStream sis;
    private static PipedOutputStream sos;

    //接收通信管道
    private static PipedInputStream ris;
    private static PipedOutputStream ros;

    public static void main(String[] args) throws Exception
    {
        DatagramSocket sendds = new DatagramSocket();
        DatagramSocket recvds = new DatagramSocket(12345);//监听的端口

        sis = new PipedInputStream();
        sos = new PipedOutputStream();
        sis.connect(sos);

        ris = new PipedInputStream();
        ros = new PipedOutputStream();
        ris.connect(ros);

        //启动发送和接收线程
        new Thread(new UdpRecv(recvds,ros)).start();
        new Thread(new UdpSend(sendds,sis)).start();

        System.out.println("Hello MyQWQ!");

        init();

        while(true)
        {
            byte[] buf = new byte[1024];
            int len = ris.read(buf);

            trecv.append(new String(buf,0,len)+"\r\n");
        }

    }

    public static void init() throws IOException
    {
        r = new Frame("MyQQ");

        trecv = new TextArea("",20,50,TextArea.SCROLLBARS_VERTICAL_ONLY);
        tsend = new TextArea("",13,50,TextArea.SCROLLBARS_VERTICAL_ONLY);

        r.setBounds(400,100,400,600);
        r.setLayout(new FlowLayout());

        r.add(trecv);
        r.add(tsend);

        //Frame事件
        event();

        r.setVisible(true);

        //设置输入框为当前焦点
        trecv.transferFocus();

    }

    public static void event()
    {
        r.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });

        tsend.addKeyListener(new KeyAdapter()
        {
            public void keyPressed(KeyEvent e)
            {
                if(e.getKeyCode()==KeyEvent.VK_ENTER)//回车键发送数据
                {
                    e.consume();
                    try
                    {
                        sos.write((tsend.getText()+"\r\n").getBytes());
                        sos.flush();
                        //System.out.println(tsend.getText());
                    }
                    catch (Exception ex)
                    {
                        throw new RuntimeException("IO错误");
                    }
                    tsend.setText("");
                }
            }
        });
    }
}

编译和打包

到文件目录下编译，也可以使用IDE建工程

javac -d . MyQQ.java
jar cvfm myqq.jar mainfest.txt myqq

运行效果

直接运行打包的myqq.jar：（由于只有一台电脑，地址写的是广播地址，能收到证明程序成功发出并收到包）