JAVA的网络通信----SOCKET

网络通信中的协议包括TCP和UDP，TCP是面向连接的可靠传输协议，在传输数据前需经过三次握手来建立连接；UDP则是尽最大努力的不可靠传输协议。

TCP的传输协议中，包括ServerSocket和Socket这两个类，ServerSocket可以通过accept()方法得到与其连接的程序的主机的套接字。

TCP的例子如下：

server:

import java.io.IOException; import java.net.*; import java.io.*; public class Server { public static void main(String[] args) throws Exception { ServerSocket server=new ServerSocket(9091); System.out.println("等待连接........"); Socket client=server.accept(); System.out.println("与client相连接....."); //String s=null; BufferedReader reader=new BufferedReader(new InputStreamReader(client.getInputStream())); PrintWriter writer=new PrintWriter(client.getOutputStream()); while(true) { String s=reader.readLine(); //System.out.println("服务器收到："+s); writer.print("服务器收到"+s+"/n"); writer.flush(); if(s.equals("end")) { break; } } client.close(); } }

client:

import java.net.*; import java.io.*; import java.util.logging.Level; import java.util.logging.Logger; public class Client { public static void main(String[] args) throws Exception { Socket server=null; server=new Socket(InetAddress.getLocalHost(),9091); BufferedReader reader1=new BufferedReader(new InputStreamReader(System.in)); PrintWriter pw=new PrintWriter(server.getOutputStream()); BufferedReader reader2=new BufferedReader(new InputStreamReader(server.getInputStream())); while(true) { String s=reader1.readLine(); pw.println(s+"/n"); pw.flush(); System.out.println(reader2.readLine()); } } }

UDP中包括DatagramSocket和DatagramPacket,如果传送端发送了，而接受方没有接收，也不会报错。这就是UDP不可靠的体现。

Send端：

import java.io.*; import java.net.*; import java.util.logging.Level; import java.util.logging.Logger; /** * * @author Administrator */ public class UDPSender { public static void main(String[] args) { try { DatagramSocket ds = new DatagramSocket(); byte[] buffer; String s="hello"; buffer=s.getBytes(); DatagramPacket dp=new DatagramPacket(buffer,buffer.length,InetAddress.getLocalHost(),3000); ds.send(dp); } catch (Exception ex) { Logger.getLogger(UDPSender.class.getName()).log(Level.SEVERE, null, ex); } } }

recieve端：

import java.net.*; import java.util.logging.Level; import java.util.logging.Logger; /** * * @author Administrator */ public class UDPRecieve { public static void main(String[] args) { try { byte[] buffer = new byte[1024]; DatagramPacket dp = new DatagramPacket(buffer, buffer.length); DatagramSocket ds = new DatagramSocket(3000); while(true) { ds.receive(dp); String s=new String(buffer,0,dp.getLength()); System.out.println(s); } } catch (Exception ex) { Logger.getLogger(UDPRecieve.class.getName()).log(Level.SEVERE, null, ex); } } }