Java Socket 编程学习之 UDP

/*
* 客户端：
* 1.创建DatagramSocket实例（一般不指定端口，而是使用动态端口）
* 2.创建用于发送数据报的非空的数据报DatagramPacket
* 3.调用DatagramSocket的send()方法发送数据报
* 4.发送完成后关闭DatagramSocket,一般用close()方法或者同try语句的自动关闭功能
*   本程序使用try语句的自动关闭功能
*/
import java.net.DatagramSocket;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Scanner;
import java.io.IOException;
import java.net.SocketException;
public class Client{
final static int SERVER_PORT = 2013;  //定义服务器端口(即数据报发往的端口)
final static int PACKET_SIZE = 1024 * 4; //定义Packet大小
public static void main(String[] args){
try(
//创建DatagramSocket实例（一般不指定端口，而是使用动态端口）
DatagramSocket clientDatagramSocket = new DatagramSocket();
//获得键盘输入
Scanner scanner = new Scanner(System.in);

){
while(scanner.hasNextLine()){//等待输入
String content = scanner.nextLine();

//创建用于发送数据报的非空的数据报DatagramPacket
//构造器：DatagramPacket(byte[] buf, int length, InetAddress address, int port)
//Constructs a datagram packet for sending packets of length length to the specified port number on the specified host.
//*注意InetAddress的用法*
//public static InetAddress getByAddress(byte[] addr) throws UnknownHostException
//Returns an InetAddress object given the raw IP address

DatagramPacket sendPacket = new DatagramPacket(content.getBytes(), content.getBytes().length,
InetAddress.getByAddress(new byte[]{(byte)202,(byte)197,(byte)145,(byte)88}), SERVER_PORT);

//调用DatagramSocket的send()方法发送数据报
clientDatagramSocket.send(sendPacket);
}

}
catch(UnknownHostException ex){
ex.printStackTrace();
}
catch(SocketException ex){
ex.printStackTrace();
}
catch(IOException ex){
ex.printStackTrace();
}
}
}

/*
* 服务端：
* 1.创建有固定IP、规定端口的DatagramSocket实例
* 2.创建用于接收客户端的数据报的空的数据报DatagramPacket
* 3.调用DatagramSocket的receive()方法接收数据报
* 4.接收完成后关闭DatagramSocket,一般用close()方法或者同try语句的自动关闭功能
*   本程序使用try语句的自动关闭功能。
*/
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.io.IOException;
public class Server{
final static int SERVER_PORT = 2013;  //定义服务器端口（服务器的接收端口）
final static int PACKET_SIZE = 1024 * 4; //定义Packet大小
public static void main(String[] args){
try(
//try语句的自动关闭
//创建有固定IP、规定端口的DatagramSocket实例
//构造器：public DatagramSocket(int port) throws SocketException
DatagramSocket serverDatagramSocket = new DatagramSocket(SERVER_PORT);
){
while(true){ //Server一直开启

//创建用于接收客户端的数据报的空的数据报DatagramPacket
//构造器：DatagramPacket(byte[] buf, int length)
//Constructs a DatagramPacket for receiving packets of length length.
DatagramPacket serverPacket = new DatagramPacket(new byte[PACKET_SIZE],PACKET_SIZE);

//用DatagramSocket的receive()方法接收数据报
//public void receive(DatagramPacket p) throws IOException
serverDatagramSocket.receive(serverPacket);

/*****************至此接收完成*****************/

/*****************下面是接收之后的处理*********/
//将packet中字节数组转换为字符串，然后输出
System.out.println(new String(serverPacket.getData(),0,serverPacket.getLength()));

}

}
catch(SocketException ex){
ex.printStackTrace();
}
catch(IOException ex){
ex.printStackTrace();
}
}
}

/*
* 客户端：
* 1.创建DatagramSocket实例（一般不指定端口，而是使用动态端口）
* 2.创建用于发送数据报的非空的数据报DatagramPacket
* 3.调用DatagramSocket的send()方法发送数据报
* 4.发送完成后关闭DatagramSocket,一般用close()方法或者同try语句的自动关闭功能
*   本程序使用try语句的自动关闭功能
*/
import java.net.DatagramSocket;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Scanner;
import java.io.IOException;
import java.net.SocketException;
public class Client{
final static int SERVER_PORT = 2013;  //定义服务器端口(即数据报发往的端口)
final static int PACKET_SIZE = 1024 * 4; //定义Packet大小
public static void main(String[] args){
try(
//创建DatagramSocket实例（一般不指定端口，而是使用动态端口）
DatagramSocket clientDatagramSocket = new DatagramSocket();
//获得键盘输入
Scanner scanner = new Scanner(System.in);

){
while(scanner.hasNextLine()){//等待输入

String content = scanner.nextLine();

//创建用于发送数据报的非空的数据报DatagramPacket
//构造器：DatagramPacket(byte[] buf, int length, InetAddress address, int port)
//Constructs a datagram packet for sending packets of length length to the specified port number on the specified host.
//*注意InetAddress的用法*
//public static InetAddress getByAddress(byte[] addr) throws UnknownHostException
//Returns an InetAddress object given the raw IP address

DatagramPacket sendToServerPacket = new DatagramPacket(content.getBytes(), content.getBytes().length,
InetAddress.getByAddress(new byte[]{(byte)202,(byte)197,(byte)145,(byte)88}), SERVER_PORT);

//调用DatagramSocket的send()方法发送数据报
clientDatagramSocket.send(sendToServerPacket);

/**************已上是客户端的发送************/

/**************下面是客户端的接收************/
//创建用于接收客户端的数据报的空的数据报DatagramPacket
//构造器：DatagramPacket(byte[] buf, int length)
//Constructs a DatagramPacket for receiving packets of length length.
DatagramPacket receiveFromServerPacket = new DatagramPacket(new byte[PACKET_SIZE],PACKET_SIZE);

//用DatagramSocket的receive()方法接收数据报
//public void receive(DatagramPacket p) throws IOException
clientDatagramSocket.receive(receiveFromServerPacket);

/*****************至此接收完成*****************/

/*****************下面是接收之后的处理*********/
//将packet中字节数组转换为字符串，然后输出
System.out.println(new String(receiveFromServerPacket.getData(),0,receiveFromServerPacket.getLength()));
}

}
catch(UnknownHostException ex){
ex.printStackTrace();
}
catch(SocketException ex){
ex.printStackTrace();
}
catch(IOException ex){
ex.printStackTrace();
}
}
}

/*
* 服务端：
* 1.创建有固定IP、规定端口的DatagramSocket实例
* 2.创建用于接收客户端的数据报的空的数据报DatagramPacket
* 3.调用DatagramSocket的receive()方法接收数据报
* 4.接收完成后关闭DatagramSocket,一般用close()方法或者同try语句的自动关闭功能
*   本程序使用try语句的自动关闭功能。
*/
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.io.IOException;
import java.util.Random;
public class Server{
final static int SERVER_PORT = 2013;  //定义服务器端口（服务器的接收端口）
final static int PACKET_SIZE = 1024 * 4; //定义Packet大小

private static String[] answers = {"AnswerOne","AnswerTwo","AnswerThree","AnswerFour"};//预定义服务器应答语句

public static void main(String[] args){
try(
//try语句的自动关闭
//创建有固定IP、规定端口的DatagramSocket实例
//构造器：public DatagramSocket(int port) throws SocketException
DatagramSocket serverDatagramSocket = new DatagramSocket(SERVER_PORT);
){
while(true){ //Server一直开启

//创建用于接收客户端的数据报的空的数据报DatagramPacket
//构造器：DatagramPacket(byte[] buf, int length)
//Constructs a DatagramPacket for receiving packets of length length.
DatagramPacket receiveFromClientPacket = new DatagramPacket(new byte[PACKET_SIZE],PACKET_SIZE);

//用DatagramSocket的receive()方法接收数据报
//public void receive(DatagramPacket p) throws IOException
serverDatagramSocket.receive(receiveFromClientPacket);

/*****************至此接收完成*****************/

/*****************下面是接收之后的处理*********/
//将packet中字节数组转换为字符串，然后输出
System.out.println(new String(receiveFromClientPacket.getData(),0,receiveFromClientPacket.getLength()));

/***************服务器发送消息*****************/
//随机应答
int random = new Random().nextInt(answers.length);  //获得0~answers.length的随机整数
//发送
//DatagramPacket(byte[] buf, int length, SocketAddress address)
//Constructs a datagram packet for sending packets of length length to the specified port number on the specified host.
//public SocketAddress getSocketAddress()
//Gets the SocketAddress (usually IP address + port number) of the remote host that this packet is being sent to or is coming from.
//从接收到的数据报中获得客户端的SocketAddress
DatagramPacket sendToClientPacket = new DatagramPacket(answers[random].getBytes(), answers[random].getBytes().length,
receiveFromClientPacket.getSocketAddress());

//调用DatagramSocket的send()方法发送数据报
serverDatagramSocket.send(sendToClientPacket);

}

}
catch(SocketException ex){
ex.printStackTrace();
}
catch(IOException ex){
ex.printStackTrace();
}
}
}