实现一个基于nio的discard server

写在前面

源码。
为了能够进一步的熟悉下nio相关的api操作，本文来实现一个基于nio的discard server。

discard server的意思是，server接收到来自client的一个消息之后，直接就将连接关闭，即discard。

1：正戏

1.1：server

package com.dahuyou.nio.discard.server.server;import java.net.InetSocketAddress;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;/*** nio discard server服务端*/
public class NioDiscardServer {public static void main(String[] args) throws Exception {// 1：打开选择器Selector selector = Selector.open();// 2：获取通道ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 3：设置为非阻塞(阻塞了也就失去了nio的意义了！并且只有非阻塞才支持绑定事件)serverSocketChannel.configureBlocking(false);// 4：绑定链接serverSocketChannel.bind(new InetSocketAddress(18899));// 5：注册io事件serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);System.out.println("服务器启动成功");// 6：阻塞方式轮询感兴趣的通道事件(IO就绪)while (selector.select() > 0) {// 7：获取封装事件+通道的选择键的集合Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {// 8：获取某个选择键进行处理SelectionKey selectionKey = iterator.next();// 9：判断具体的事件，并进行处理if (selectionKey.isAcceptable()) {System.out.println("新连接来了：" + selectionKey.channel());// 10：就绪事件，获取客户端的链接(一个个来建立链接？？？可能不是个问题！！！不太明白这里为什么// 这么写？？？)SocketChannel socketChannel = serverSocketChannel.accept();// 11：设置为非阻塞socketChannel.configureBlocking(false);// 12：注册到选择器监听相关事件
//                    SelectionKey register = socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE | SelectionKey.OP_CONNECT);socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE | SelectionKey.OP_CONNECT);}// 可写事件if (selectionKey.isWritable()) {System.out.println("可写啦，" + selectionKey.channel());}if (selectionKey.isConnectable()) {System.out.println("连接成功啦，" + selectionKey.channel());}if (selectionKey.isReadable()) {System.out.println("数据可读啦，" + selectionKey.channel());// 13：获取通道，为读取数据做准备啦SocketChannel socketChannel = (SocketChannel) selectionKey.channel();// 14：读取数据啦ByteBuffer byteBuffer = ByteBuffer.allocate(1024);int length = 0;while ((length = socketChannel.read(byteBuffer)) > 0) {// 转成读模式byteBuffer.flip();System.out.println("读取到数据：" + new String(byteBuffer.array(), 0, length));// 恢复成写模式(这里其实不用的，但当个好习惯吧！)byteBuffer.clear();}// 读完消息了，就discard(discard server的体现指出)socketChannel.close();}// 15：移出选择键，防止重复处理iterator.remove();}}System.out.println("discard 啦！！！！！！！！！！！！");// 关闭链接(这里应该是执行不到的，因为selector.select啦)serverSocketChannel.close();}}

代码socketChannel.close();在read消息后，就discard啦！另外，关键步骤的代码看带标号的。

1.2：client

package com.dahuyou.nio.discard.server.client;import io.netty.buffer.ByteBuf;import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;public class NioDiscardClient {public static void main(String[] args) throws Exception {InetSocketAddress inetSocketAddress= new InetSocketAddress("127.0.0.1", 18899);// 1：获取通道SocketChannel socketChannel = SocketChannel.open(inetSocketAddress);// 2：切换成非阻塞socketChannel.configureBlocking(false);// 不断自旋，等待连接完成while (!socketChannel.finishConnect()) {}System.out.println("链接server成功");// 3：创建缓冲区，填充数据，并向通道写入数据ByteBuffer byteBuffer = ByteBuffer.allocate(1024);byteBuffer.put("hello discard server".getBytes());// 转成读模式,开始读数据写出去byteBuffer.flip();socketChannel.write(byteBuffer);System.out.println("向server写数据done");// 关了，释放资源，好习惯socketChannel.shutdownOutput();socketChannel.close();}
}