通信Socket

通过URL读取网页内容
    1通过URL对象的openStream（）方法可以得到指定资源的输入流。
    2通过输入流可以读取、访问网络上的数据。

    案例：

   import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;


public class UrlTest {
       public static void main(String[] args) {
		try {
			URL url = new URL("http://www.baidu.com");
		    InputStream is = url.openStream();
		    InputStreamReader isr = new InputStreamReader(is,"utf-8");
		    BufferedReader br = new BufferedReader(isr);
		    String data = br.readLine();
		    while(data != null){
		    	System.out.println(data);
		    	data = br.readLine();
		    }
		    br.close();
		    isr.close();
		    is.close();
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

Socket通信实现步骤
   1 创建ServerSocekt和Socket
   2 打开连接到Socket的输入/输出流
   3 按照协议对Socket进行读写操作
   4关闭输入输出流、关闭Socket


   基于TCP的Socket通信
   客户端能够相应，
    服务端：

 import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;


public class Server {
       public static void main(String[] args) {
		try {
			ServerSocket serverSocket = new ServerSocket(8888);
			System.out.println("服务器端即将启动！！");
			Socket socket = serverSocket.accept();
			InputStream is = socket.getInputStream();
			InputStreamReader isr = new InputStreamReader(is);
			BufferedReader br = new BufferedReader(isr);
			String info = null;
			while((info = br.readLine()) != null){
				System.out.println("我是服务器，客户端说：" + info);
			}
			socket.shutdownInput();
			OutputStream os = socket.getOutputStream();
			PrintWriter pw = new PrintWriter(os);
			pw.write("欢迎您！！");
			pw.flush();
			
			pw.close();
			os.close();
			br.close();
			isr.close();
			is.close();
			socket.close();
			serverSocket.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

客户端：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;


public class Client {
        public static void main(String[] args) {
			try {
				Socket socket = new Socket("localhost",8888);
				OutputStream os = socket.getOutputStream();
				PrintWriter pw = new PrintWriter(os);
				pw.write("用户名：admin;密码:123");
				pw.flush();
				socket.shutdownOutput();
				
				InputStream is = socket.getInputStream();
				BufferedReader br = new BufferedReader(new InputStreamReader(is));
				String info = null;
				while((info = br.readLine()) != null){
					System.out.println("我是客户端，服务器说：" + info);
				}
				
				br.close();
				is.close();
				pw.close();
				os.close();
				socket.close();
			} catch (UnknownHostException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
		}
}

多线程服务器与多客户端通信：
   基本实现步骤：
        1 服务器端创建ServerSocket，循环调用accept（）等待客户端连接
2 客户端创建一个socket并请求和服务端连接
3 服务端接受客户端请求，创建socket与客户建立专线连接
4 建立连接的两个socket在一个单独的线程对话
5 服务器端继续等待新的连接
案例：

 import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;


public class ServerThread extends Thread{
	Socket socket = null;
	public ServerThread(Socket socket){
		this.socket = socket;
	}
	public void run(){
		
		InputStream is= null;
		InputStreamReader isr = null;
		BufferedReader br = null;
		OutputStream os = null;
		PrintWriter pw = null;
		try {
			is = socket.getInputStream();
			isr = new InputStreamReader(is);
			br = new BufferedReader(isr);
			String info = null;
			while((info = br.readLine()) != null){
				System.out.println("我是服务器，客户端说：" + info);
			}
			socket.shutdownInput();
			os = socket.getOutputStream();
			pw = new PrintWriter(os);
			pw.write("欢迎您！！");
			pw.flush();
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
				try {
					if(pw!= null)
						pw.close();
					if(os != null)
						os.close();
					if(br != null)
						br.close();
					if(isr != null)
						isr.close();
					if(is != null)
						is.close();
					if(socket != null)
						socket.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
		}
//		serverSocket.close();
	}

}

服务端：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;


public class Server {
       public static void main(String[] args) {
		try {
			ServerSocket serverSocket = new ServerSocket(8888);
			Socket socket = null;
			int count = 0;
			System.out.println("服务器端即将启动！！");
            while(true){
            	socket = serverSocket.accept();
            	ServerThread serverThread = new ServerThread(socket);
            	serverThread.start();
            	count++;
            	System.out.println("客户端连接数量：" + count);
               InetAddress address = socket.getInetAddress();
               System.out.println("当前客户端的IP：" + address);
            }
            
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

客户端同上。

UDP
     DatagramPacket:表示数据报包
     DatagramSocket：进行端到端通信的类
基于UDP的Socket编程
   服务端：

 package com.hpu.lianxi;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class UDPServer {
      public static void main(String[] args) throws IOException {
		DatagramSocket socket = new DatagramSocket(8800);
		byte[] data = new byte[1024];
		System.out.println("服务器已经启动，等待客户端发送数据****");
		DatagramPacket packet = new DatagramPacket(data,data.length);
	    socket.receive(packet);
	    String info = new String(data,0,packet.getLength());
	    System.out.println("这是服务端，客户端说：" + info);
	    
	    InetAddress address = packet.getAddress();
	    int port = packet.getPort();
	    byte[] data2 = "欢迎您！！".getBytes();
	    DatagramPacket packet2 = new DatagramPacket(data2, data2.length,address,port);
	    
	    socket.send(packet2);
	    socket.close();
      }
} 

客户端：

 package com.hpu.lianxi;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

public class UDPClient {
         public static void main(String[] args) throws IOException {
			InetAddress address = InetAddress.getByName("localhost");
			int port = 8800;
			byte[] data = "用户名:admin;密码：123".getBytes();
			DatagramPacket packet = new DatagramPacket(data, data.length,address,port);
			DatagramSocket socket = new DatagramSocket();
			socket.send(packet);
			
			byte[] data2 = new byte[1024];
			DatagramPacket packet2 = new DatagramPacket(data2, data2.length,address,port);
			socket.receive(packet2);
			String reply = new String(data2,0,packet2.getLength());
			System.out.println("我是客户端，服务器说：" + reply);
			socket.close();
		}
}

 多线程的优先级
    如果不设置优先级可能会导致运行时速度非常慢，可降低优先级
    输入流与输出流的关闭
    对于同一个socket，如果关闭了输出流，则与该输出流关联的socket也会被关闭，所以一般不用
    关闭流，直接关闭socket即可