IP地址和端口号组成了所谓的Socket，Socket是网络上运行的程序之间双向通信链路的终结点，是TCP和UDP的基础。
Java中对于网络通信的支持主要包含以下四大类：
1.InetAddress：用于标识网络上的硬件资源。说白了就是标识IP等。
2.URL：统一资源定位符，通过URL可以直接读取或写入网络上的数据。
3.Sockets：使用TCP协议实现网络通信的Socket相关的类。
4.Datagram：使用UDP协议，将数据保存在数据报中，通过网络进行通信。
简单的两个DEMO，介绍java中的InetAddress类和URL类。
介绍InetAddress类：
package com.wang;import java.net.InetAddress;import java.net.UnknownHostException;import java.util.Arrays;publicclassInetAddressTest{publicstaticvoid main(String[] args)throwsUnknownHostException{InetAddress localhost =InetAddress.getLocalHost();System.out.println("localhost:"+ localhost);InetAddress address =InetAddress.getByName("wangdaye-PC");System.out.println(address.getHostAddress()+"="+ address.getHostName());byte[] bytes = address.getAddress();System.out.println("字节数组："+Arrays.toString(bytes));System.out.println(address);}}
介绍URL类：
package com.wang;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.net.URL;/*** 端口号未指定，默认为80，getPort()函数返回值为-1* @author wangdaye*/publicclassURLTest{publicstaticvoid main(String[] args)throwsException{URL testUrl =new URL("http://www.sina.com:80/sb/index.jsp");// System.out.println(testUrl.getPort());URL url =new URL(testUrl,"wang");System.out.println("协议："+ url.getProtocol());System.out.println("主机名："+ url.getHost());System.out.println("端口："+ url.getPort());System.out.println("文件路径："+ url.getPath());System.out.println("文件名称："+ url.getFile());System.out.println("相对路径："+ url.getRef());System.out.println("查询字符串："+ url.getQuery());//读取网络资源的内容URL baidu =new URL("http://www.baidu.com:80/sb/index.jsp");InputStream inputStream = baidu.openStream();InputStreamReader reader =newInputStreamReader(inputStream);BufferedReader br =newBufferedReader(reader);while(br.ready()){String sb = br.readLine();System.out.println(sb);}}}
基于TCP的socket通信的Demo：
服务端：
package com.wangdaye.socketIO;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.ServerSocket;import java.net.Socket;/*** 基于TCP通信的socket服务器端* @author wangdaye**/publicclassTCPServer{publicstaticvoid main(String[] args){try{//1.创建服务器端socket，即serverSocket，指定绑定端口，并监听此端口。ServerSocket serverSocket =newServerSocket(8888);System.out.println("*************服务器即将启动，等待客户端链接*******************");//2.调用accept()方法开始监听，等待客户端连接，此时处于阻塞状态。Socket socket = serverSocket.accept();//3.获取输入流，读取客户端信息InputStream inputStream = socket.getInputStream();InputStreamReader reader =newInputStreamReader(inputStream);BufferedReader br =newBufferedReader(reader);String sb =null;while((sb = br.readLine())!=null){System.out.println("客户端说："+ sb);}socket.shutdownInput();//关闭输入流//4.关闭资源br.close();reader.close();inputStream.close();socket.close();serverSocket.close();}catch(IOException e){// TODO Auto-generated catch blocke.printStackTrace();}}}
客户端：
package com.wangdaye.socketIO;import java.io.IOException;import java.io.OutputStream;import java.io.PrintWriter;import java.net.Socket;import java.net.UnknownHostException;/*** 基于TCP通信的socket客户端* @author wangdaye**/publicclassTCPClient{publicstaticvoid main(String[] args){try{//1.创建客户端socket，并指定服务器地址和端口Socket socket =newSocket("localhost",8888);//2.获取输出流，向服务器端发送信息OutputStream outputStream = socket.getOutputStream();//字节输出流PrintWriter pw =newPrintWriter(outputStream);//将输出流打包成打印流pw.write("用户名：sb，密码：123");pw.flush();socket.shutdownOutput();//3.关闭资源outputStream.close();socket.close();}catch(UnknownHostException e){e.printStackTrace();}catch(IOException e){e.printStackTrace();}}}
多线程服务端：
package com.wangdaye.socketIO;import java.net.ServerSocket;import java.net.Socket;publicclassTCPThreadServer{publicstaticvoid main(String[] args)throwsException{ServerSocket serverSocket =newServerSocket(8888);System.out.println("***********************服务器启动成功，正在等待客户端连接*********************");Socket socket =null;int count =0;while(true){socket = serverSocket.accept();count++;System.out.println("当前客户端连接数量："+ count);System.out.println("当前客户端IP地址是："+ socket.getInetAddress()+",主机名:"+socket.getInetAddress().getHostAddress()+":"+ socket.getPort());ServerThread serverThread =newServerThread(socket);serverThread.run();}}}
基于UDP的Socket通信的Demo:
服务端：
package com.wangdaye.socketIO.udp;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;publicclassServerUdp{publicstaticvoid main(String[] args)throwsException{System.out.println("***************服务端已经启动，正在等待客户端发送数据*************");//接收客户端发送的数据//1.创建服务器端DatagramSocket，指定端口号DatagramSocket datagramSocket =newDatagramSocket(8800);//2.创建数据报，接收客户端发送的数据,指定数据包大小byte[] b =newbyte[1024];DatagramPacket datagramPacket =newDatagramPacket(b,b.length);//3.接收客户端发送的数据datagramSocket.receive(datagramPacket);//此方法在接收到数据之前会一直阻塞//4.查看客户端发送的信息,读取数据String str =newString(b,0, datagramPacket.getLength());System.out.println("我是服务器，客户端说:"+ str);//向客户端响应数据//1.获取客户端地址和端口InetAddress clientAddress=datagramPacket.getAddress();int clientPort = datagramPacket.getPort();String sb ="欢迎你，客户端";byte[] bytes = sb.getBytes();//2.创建要向客户端发送的数据DatagramPacket dp =newDatagramPacket(bytes,bytes.length,clientAddress,clientPort);//3.响应客户端datagramSocket.send(dp);//4.关闭连接datagramSocket.close();}}
客户端：
package com.wangdaye.socketIO.udp;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;publicclassClientUdp{publicstaticvoid main(String[] args)throwsException{//向服务器端发送数据//1.定义服务器的地址、端口号InetAddress inetAddress =InetAddress.getByName("localhost");int port =8800;String msg ="我是客户端，我了个去~";byte[] bytes = msg.getBytes();//2.创建数据报，包含发送的消息DatagramPacket packet =newDatagramPacket(bytes,bytes.length,inetAddress,port);//3.创建DatagramSocket对象DatagramSocket socket =newDatagramSocket();//4.发送数据socket.send(packet);//接收服务端响应数据//1.创建数据包，接收服务端响应数据byte[] receivedBytes =newbyte[1024];DatagramPacket dp =newDatagramPacket(receivedBytes,receivedBytes.length);//2.接收服务器端响应数据socket.receive(dp);//3.读取数据String reply =newString(receivedBytes,0,receivedBytes.length);System.out.println(reply);//4.关闭资源socket.close();}}
注意：
1.生产环境下，对线程的优先级做一个控制，否则会效率低下
2.输入输出流的关闭问题，关闭了socket，流也就关闭了
3.传递对象，平时都是以字符串传递的
4.传递文件