Netty学习之二--Java socket编程（UDP实例）
（TCP）传输控制协议，是一种提供可靠数据传输的通用协议,由于TCP需要建立真实的连接，所以需要消耗服务器的负载要大于UDP
（UDP）用户数据报协议，是一个面向无连接的协议。采用该协议不需要两个应用程序先建立连接。UDP协议不提供差错恢复，不能提供数据重传，因此该协议传输数据安全性差。
2.UDP 编程
1.服务器代码
package com.ly.netty.scoket.N03.server;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
public class Server {
private byte[] buf = new byte[1024];
private DatagramPacket dp_receive = new DatagramPacket(buf, buf.length);
public Server() {
try {
//客户端在8888端口监听接收到的数据
DatagramSocket socket = new DatagramSocket(8888);
System.out.println("Server started!");
boolean f = true;
while (f) {
socket.receive(dp_receive);
//接收到客户端的消息
String str_receive = new String(dp_receive.getData(),0,dp_receive.getLength()) +
" from " + dp_receive.getAddress().getHostAddress() + ":" + dp_receive.getPort();
System.out.println(str_receive);
String str_send = "Hello I am server!" ;
DatagramPacket dp_send= new DatagramPacket(str_send.getBytes(),str_send.length(),dp_receive.getAddress(),9000);
socket.send(dp_send);
}
socket.close();
} catch (SocketException e) {
System.err.println("Can't open socket");
System.exit(1);
} catch (IOException e) {
System.err.println("Communication error");
e.printStackTrace();
}
}
public static void main(String[] args) {
new Server();
}
}
2.客户端代码
package com.ly.netty.scoket.N03.client;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Client {
private byte[] buf = new byte[1024];
private static final int TIMEOUT = 1000; // 设置接收数据的超时时间
private static final int MAXNUM = 10; // 设置重发数据的最多次数
private void sendMessage(String msg) throws Exception {
// 客户端在9000端口监听接收到的数据
DatagramSocket ds = new DatagramSocket(8889);
InetAddress loc = InetAddress.getLocalHost();
// 定义用来发送数据的DatagramPacket实例
DatagramPacket dp_send = new DatagramPacket(msg.getBytes(),
msg.length(), loc, 8888);
// 定义用来接收数据的DatagramPacket实例
DatagramPacket dp_receive = new DatagramPacket(buf, 1024);
// 数据发向本地9000端口
ds.setSoTimeout(TIMEOUT); // 设置接收数据时阻塞的最长时间
int tries = 0; // 重发数据的次数
boolean response = false; // 是否接收到数据的标志位
// 直到接收到数据，或者重发次数达到预定值，则退出循环
while (!response && tries < MAXNUM) {
// 发送数据
ds.send(dp_send);
try {
ds.receive(dp_receive);
// 如果接收到的数据不是来自目标地址，则抛出异常
if (!dp_receive.getAddress().equals(loc)) {
throw new IOException(
"Received packet from an umknown source");
}
// 如果接收到数据。则将receivedResponse标志位改为true，从而退出循环
response = true;
} catch (Exception e) {
// 如果接收数据时阻塞超时，重发并减少一次重发的次数
tries += 1;
System.out.println("Time out," + (MAXNUM - tries)
+ " more tries...");
}
}
if (response) {
String str_receive = new String(dp_receive.getData(), 0,
dp_receive.getLength())
+ " from "
+ dp_receive.getAddress().getHostAddress()
+ ":"
+ dp_receive.getPort();
System.out.println(str_receive);
System.out.println(str_receive);
// 由于dp_receive在接收了数据之后，其内部消息长度值会变为实际接收的消息的字节数，
// 所以这里要将dp_receive的内部消息长度重新置为1024
dp_receive.setLength(1024);
}else{
//如果重发MAXNUM次数据后，仍未获得服务器发送回来的数据，则打印如下信息
System.out.println("No response!");
}
ds.close();
}
public static void main(String[] args) throws Exception {
Client client = new Client();
String msg = "Hello I am client!";
client.sendMessage(msg);
}
}
参考文献:
http://blog.csdn.net/qq_23473123/article/details/51464272
http://blog.csdn.net/ns_code/article/details/14128987