package com.crow;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.net.ServerSocket;

import java.nio.ByteBuffer;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.util.Iterator;

import java.util.Set;

/**

* Created by CrowHawk on 17/9/4.

*/

public class MultiPortEcho {

private int ports[];

private ByteBuffer echoBuffer = ByteBuffer.allocate( 1024 );

public MultiPortEcho( int ports[] ) throws IOException {

this.ports = ports;

go();

}

private void go() throws IOException {

Selector selector = Selector.open();

// Open a listener on each port, and register each one

// with the selector

for (int i=0; i < ports.length; i++) {

ServerSocketChannel ssc = ServerSocketChannel.open();

ssc.configureBlocking(false);

ServerSocket ss = ssc.socket();

InetSocketAddress address = new InetSocketAddress(ports[i]);

ss.bind(address);

//将新打开的 ServerSocketChannels 注册到 Selector上，指定监听accept事件

SelectionKey key = ssc.register(selector, SelectionKey.OP_ACCEPT);

System.out.println("Going to listen on " + ports[i]);

}

while (true) {

int num = selector.select();//返回该选择器中对I/O事件准备就绪的channel对应的key的数量

Set selectedKeys = selector.selectedKeys();//返回key的集合

Iterator it = selectedKeys.iterator();

while (it.hasNext()) {//遍历key集合，集合中的元素为SelectionKey类型

SelectionKey key = (SelectionKey) it.next();

if ((key.readyOps() & SelectionKey.OP_ACCEPT)

== SelectionKey.OP_ACCEPT) {//检查发生了什么类型的事件

// Accept the new connection

ServerSocketChannel ssc = (ServerSocketChannel)key.channel();

SocketChannel sc = ssc.accept();

sc.configureBlocking( false );

// Add the new connection to the selector

SelectionKey newKey = sc.register( selector, SelectionKey.OP_READ );//监听read事件

//Selector不会自己从已选择键集中移除SelectionKey实例。必须在处理完通道时自己移除。下次该通道变成就绪时，Selector会再次将其放入已选择键集中。

it.remove();

System.out.println( "Got connection from "+sc );

}else if ((key.readyOps() & SelectionKey.OP_READ)

== SelectionKey.OP_READ) {

// Read the data

SocketChannel sc = (SocketChannel)key.channel();

// Echo data

int bytesEchoed = 0;

while (true) {

echoBuffer.clear();

int r = sc.read( echoBuffer );

if (r<=0) {

break;

}

echoBuffer.flip();

sc.write( echoBuffer );

bytesEchoed += r;

}

System.out.println( "Echoed "+bytesEchoed+" from "+sc );

it.remove();

}

}

}

}

public static void main( String args[] ) throws Exception {

if (args.length<=0) {

System.err.println( "Usage: java MultiPortEcho port [port port ...]" );

System.exit( 1 );

}

int ports[] = new int[args.length];

for (int i=0; i<args.length; ++i) {

ports[i] = Integer.parseInt( args[i] );

}

new MultiPortEcho( ports );

}

}