第四章、java中Socket的用法

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1.普通Socket的用法

　　java中的通信时通过Socket实现的，Socket分为ServerSocket和Socket两大类。ServerSocket用于服务端，可以通过accept方法监听请求，监听到请求后返回Socket，Socket用于具体完整的数据传输，客户端直接使用Socket发起请求并传输数据。

　　服务端代码

package com.roy.socket;

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

public class Server {
	public static void main(String[] args) {
		try {
			//创建一个ServerSocket监听8080端口
			ServerSocket serverSocket = new ServerSocket(8080);
			//等待请求，阻塞
			Socket socket = serverSocket.accept();
			//接受到请求后是同socket进行通信，创建BufferedReader用于读取数据
			//InputStreamReader可以转换字节流为字符流
			BufferedReader is = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			String line = is.readLine();
			System.out.println("received from client: "+ line);
			//创建printWriter，用于发送数据
			PrintWriter pWriter = new PrintWriter(socket.getOutputStream());
			pWriter.println("received data: " + line);
			pWriter.flush();
			//关闭资源
			pWriter.close();
			is.close();
			socket.close();
			serverSocket.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

　　客户端代码

package com.roy.socket;

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

public class Client {
	public static void main(String[] args) {
		String msg = "Client data";
		try {
			//创建一个Socket
			Socket socket = new Socket("127.0.0.1", 8080);
			//使用Socket创建printwriter和bufferedReader进行读写数据
			PrintWriter printWriter = new PrintWriter(socket.getOutputStream());
			BufferedReader is = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			printWriter.println(msg);
			printWriter.flush();
			String line = is.readLine();
			System.out.println("received from server: " + line);
			printWriter.close();
			is.close();
			socket.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

2.NioSocket的用法

　　nio提供了相应的工具Serve和SocketChannel，它们分别对应原来的ServerSocket和Socket。

　　Buffer、Channel、Slector理解：NioSocket模式相当于现在的电商快递模式。Buffer就是要送的货物，Channel就是送货员（或者开往某个区域的配货车），Selector就是中转站的分捡员。

package com.roy.niosocket;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
public class NIOServer {
	public static void main(String[] args) {
		//创建ServerSocketChannel，监听8080端口
	
		try {
			ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
			serverSocketChannel.socket().bind(new InetSocketAddress(8080));
			//设置为非阻塞
			serverSocketChannel.configureBlocking(false);
			//为serverSocketChannel注册选择器
			Selector selector = Selector.open();
			serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
			//创建处理器
			Handler handler = new Handler(1024);
			while(true){
				//等待请求，每次等待阻塞3秒，超过3秒后线程继续向下执行，如果传入0或者不传参数则将一直阻塞
				if(selector.select(3000)==0){
					System.out.println("等待请求超时-----");
					continue;
				}
				System.out.println("处理请求----------");
				//获取处理的selectionKey
				Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
				while(keyIter.hasNext()){
					SelectionKey key = keyIter.next();
					try {
						//接受到连接请求时
						if (key.isAcceptable()) {
							handler.handleAccept(key);
						}
						//读数据
						if (key.isReadable()) {
							handler.handleReader(key);
						}
					} catch (Exception e) {
						keyIter.remove();
						continue;
					}
					//处理完成后，从待处理的SelectionKey迭代器中移除当前所使用的key
					keyIter.remove();
				}
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	private static class Handler{
		private int bufferSize = 1024;
		private String localCharset = "UTF-8";
		public Handler() {
			// TODO Auto-generated constructor stub
		}
		public Handler(int bufferSize) {
			this(bufferSize,null);
		}
		public Handler(String localCharset) {
			this(-1,localCharset);
		}
		public Handler(int bufferSize,String localCharset){
			if(bufferSize>0){
				this.bufferSize = bufferSize;
			}
			if(localCharset!=null){
				this.localCharset = localCharset;
			}
		}
		public void handleAccept(SelectionKey key) throws IOException{
			SocketChannel sc = ((ServerSocketChannel)key.channel()).accept();
			sc.configureBlocking(false);
			sc.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufferSize));
		}
		public void handleReader(SelectionKey key) throws IOException{
			//获取channel
			
			SocketChannel sc = (SocketChannel) key.channel();
			//获取buffer并重置
			ByteBuffer buffer =(ByteBuffer) key.attachment();
			buffer.clear();
			//没有读到内容则关闭
			if (sc.read(buffer)==-1) {
				sc.close();
			}else {
				//将buffer转换为读状态
				buffer.flip();
				//将buffer中接受到的值按localCharset格式编码后保存到receivedString
				String receivedString = Charset.forName(localCharset).newDecoder().decode(buffer).toString();
				System.out.println("received from client :" + receivedString);
				
				//返回数据给客户端
				String sendString = "received data: "+receivedString;
				buffer = ByteBuffer.wrap(sendString.getBytes(localCharset));
				sc.write(buffer);
				//关闭socket
				sc.close();
			}
			
		}
	}
}

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