javaudp代码

‘壹’ 请教大神，怎么使用java实现UDP端口扫描

给你个UDP服务端与客户端的示例:

服务端代码:

importjava.net.DatagramPacket;
importjava.net.InetAddress;
importjava.net.MulticastSocket;

publicclassUDPMulticastServer{
	finalstaticintRECEIVE_LENGTH=1024;

	staticStringmulticastHost="224.0.0.1";

	staticintlocalPort=9998;

	publicstaticvoidmain(String[]args)throwsException{

		InetAddressreceiveAddress=InetAddress.getByName(multicastHost);

		if(!receiveAddress.isMulticastAddress()){//测试是否为多播地址

			thrownewException("请使用多播地址");

		}

		intport=localPort;

		=newMulticastSocket(port);

		receiveMulticast.joinGroup(receiveAddress);

		
		booleanisStop=false;
		while(!isStop){
			DatagramPacketdp=newDatagramPacket(newbyte[RECEIVE_LENGTH],RECEIVE_LENGTH);
			receiveMulticast.receive(dp);
			Stringdata=newString(dp.getData()).trim();
			System.out.println(data);
			if("exit".equals(data)){
				System.out.println("程序退出");
				isStop=true;
			}
		}

		receiveMulticast.close();
	}
}

客户端代码:

importjava.net.DatagramPacket;
importjava.net.InetAddress;
importjava.net.MulticastSocket;

publicclassUDPMulticastClient{
	staticStringdestAddressStr="224.0.0.1";
	
staticintdestPortInt=9998;

staticintTTLTime=4;

publicstaticvoidmain(String[]args)throwsException{	InetAddressdestAddress=InetAddress.getByName(destAddressStr);

	if(!destAddress.isMulticastAddress()){//检测该地址是否是多播地址
	
	thrownewException("地址不是多播地址");
	
	}

	intdestPort=destPortInt;
	
	
	MulticastSocketmultiSocket=newMulticastSocket();
	
//	intTTL=TTLTime;
//	multiSocket.setTimeToLive(TTL);
	
	byte[]sendMSG="exit".getBytes();
	
	DatagramPacketdp=newDatagramPacket(sendMSG,sendMSG.length,destAddress,destPort);
	
	multiSocket.send(dp);
	
	multiSocket.close();
	
	}

}

‘贰’ 我要一份用java网络编程写的点对点的两人聊天程序(TCP和UDP)

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
}
}
}

‘叁’ 关于java UDP方面的一些问题

看你的程序好像要实现多点传输（多播组）， 可以参考MulticastSocket，也是基于UDP协议的 ，可以自动广播数据到连接上的客户端，不用等待每个客户端都要复制。那样如果数据量大，客户端多就太耗资源了。