JAVA UDP聊天程序问题 给100分！

public void run() /* 用于被调用的接口run方法 */

{

while (true)

{

try

{

byte[] buf = new byte[1024]/* 接收端程序，设置BUF数组长度为1024位 */

DatagramPacket dp = new DatagramPacket(buf, buf.length)/* 创建接收数据报的实例 */

ds.receive(dp)

lst.add("他说:" + new String(buf), 0)

} catch (IOException ex)

{

}

}

}

======================

线程的run方法改成上面这样就可以了，原因是因为接收端每次循环都是使用的同一个buf，而buf没有清空，所以导致每次接收都只更新前面一小段信息，后面的信息没有改变。

使用DatagramSocket和DatagramPacket

其中DatagramSocket使用一个发送的端口号

DatagramPacket的参数

DatagramPacket(bytes[] bytes,int bytes[].length,InetAddress ip, int port)里的port就是目标端口

要向两个端口号发送，需要创建两个DatagramPacket，分别填写两个IP地址和端口号，并用DatagramSocket发送。

另外两个端口需要做监听

要注意ip要为局域网可以畅通无阻，广域网可能导致网管阻止

下面是个例子，发两遍即可。

int SERVER_PORT=7000

String severIp="192.168.1.100"

DatagramSocket clientSocket

try

{

InetAddress local = InetAddress.getByName(severIp)

DatagramPacket dPacket

clientSocket = new DatagramSocket

dPacket = new DatagramPacket("Hello".getBytes("utf-8"),"Hello".getBytes("utf-8").length,

local, SERVER_PORT)

clientSocket.send(dPacket)//这里是发送

byte[] msg = new byte[11246]

DatagramPacket rPacket = new DatagramPacket(msg, msg.length)

clientSocket.receive(rPacket)//这里是接收监听

}

catch (IOException e)

{

e.printStackTrace()

}

clientSocket.close()

Server端：

import java.io.*

import java.net.*

import java.applet.Applet

public class TalkServer{

public static void main(String args[]) {

try{

ServerSocket server=null

try{

server=new ServerSocket(4700)

}catch(Exception e) {

System.out.println("can not listen to:"+e)

}

Socket socket=null

try{

socket=server.accept()

}catch(Exception e) {

System.out.println("Error."+e)

}

String line

BufferedReader is=new BufferedReader(new InputStreamReader(socket.getInputStream()))

PrintWriter os=new PrintWriter(socket.getOutputStream())

BufferedReader sin=new BufferedReader(new InputStreamReader(System.in))

System.out.println("Client:"+is.readLine())

line=sin.readLine()

while(!line.equals("bye")){

os.println(line)

os.flush()

System.out.println("Server:"+line)

System.out.println("Client:"+is.readLine())

line=sin.readLine()

}

os.close()

is.close()

socket.close()

server.close()

}catch(Exception e){

System.out.println("Error:"+e)

}

}

}

Client端：

import java.io.*

import java.net.*

public class TalkClient {

public static void main(String args[]) {

try{

Socket socket=new Socket("127.0.0.1",4700)

BufferedReader sin=new BufferedReader(new InputStreamReader(System.in))

PrintWriter os=new PrintWriter(socket.getOutputStream())

BufferedReader is=new BufferedReader(new InputStreamReader(socket.getInputStream()))

String readline

readline=sin.readLine()//从系统标准输入读入一字符串

while(!readline.equals("bye")){

os.println(readline)

os.flush()

System.out.println("Client:"+readline)

System.out.println("Server:"+is.readLine())

readline=sin.readLine()//从系统标准输入读入一字符串

}

os.close()//关闭Socket输出流

is.close()//关闭Socket输入流

socket.close()//关闭Socket

}catch(Exception e) {

System.out.println("Error"+e)//出错，则打印出错信息

}

}

}

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