package com.cnblogs.gpcuster;
import java.nio.channels.SelectionKey;
import java.io.IOException;
public interface TCPProtocol {
      void handleAccept(SelectionKey key) throws IOException;
      void handleRead(SelectionKey key) throws IOException;
      void handleWrite(SelectionKey key) throws IOException;
}

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.util.Iterator;
public class TCPServerSelector {
      private static final int BUFSIZE = 256;// Buffersize(bytes)
      private static final int TIMEOUT = 3000;// Waittimeout(milliseconds)
      public static void main(String[] args) throws IOException {
            if (args.length < 1) {// Testforcorrect#ofargs
                  throw new IllegalArgumentException("Parameter(s):<Port>...");
            }
            // Createaselectortomultiplexlisteningsocketsandconnections
            Selector selector = Selector.open();
            // Createlisteningsocketchannelforeachportandregisterselector
            for (String arg : args) {
                  ServerSocketChannel listnChannel = ServerSocketChannel.open();
                  listnChannel.socket().bind(
                  new InetSocketAddress(Integer.parseInt(arg)));
                  listnChannel.configureBlocking(false);// mustbenonblockingtoregister
                  // Registerselectorwithchannel.Thereturnedkeyisignored
                  listnChannel.register(selector, SelectionKey.OP_ACCEPT);
            }
            // Createahandlerthatwillimplementtheprotocol
            TCPProtocol protocol = new EchoSelectorProtocol(BUFSIZE);
            while (true) {// Runforever,processingavailableI/Ooperations
                  // Waitforsomechanneltobeready(ortimeout)
                  if (selector.select(TIMEOUT) == 0) {// returns#ofreadychans
                        System.out.print(".");
                        continue;
                  }
                  // GetiteratoronsetofkeyswithI/Otoprocess
                  Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
                  while (keyIter.hasNext()) {
                        SelectionKey key = keyIter.next();// Keyisbitmask
                        // Serversocketchannelhaspendingconnectionrequests?
                        if (key.isAcceptable()) {
                              protocol.handleAccept(key);
                        }
                        // Clientsocketchannelhaspendingdata?
                        if (key.isReadable()) {
                              protocol.handleRead(key);
                        }
                        // Clientsocketchannelisavailableforwritingand
                        // keyisvalid(i.e.,channelnotclosed)?
                        if (key.isValid() && key.isWritable()) {
                              protocol.handleWrite(key);
                        }
                        keyIter.remove();// removefromsetofselectedkeys
                  }
            }
      }
}

package com.cnblogs.gpcuster;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.ByteBuffer;
import java.io.IOException;
public class EchoSelectorProtocol implements TCPProtocol {
      private int bufSize;// SizeofI/Obuffer
      public EchoSelectorProtocol(int bufSize) {
            this.bufSize = bufSize;
      }
      public void handleAccept(SelectionKey key) throws IOException {
            SocketChannel clntChan = ((ServerSocketChannel) key.channel()).accept();
            clntChan.configureBlocking(false);// Mustbenonblockingtoregister
            // Registertheselectorwithnewchannelforreadandattachbytebuffer
            clntChan.register(key.selector(), SelectionKey.OP_READ, ByteBuffer
            .allocate(bufSize));
      }
      public void handleRead(SelectionKey key) throws IOException {
            // Clientsocketchannelhaspendingdata
            SocketChannel clntChan = (SocketChannel) key.channel();
            ByteBuffer buf = (ByteBuffer) key.attachment();
            long bytesRead = clntChan.read(buf);
            if (bytesRead == -1) {// Didtheotherendclose?
                  clntChan.close();
            } else if (bytesRead > 0) {
                  // Indicateviakeythatreading/writingarebothofinterestnow.
                  key.interestOps(SelectionKey.OP_READ SelectionKey.OP_WRITE);
            }
      }
      public void handleWrite(SelectionKey key) throws IOException {
            /*
            * Channelisavailableforwriting,andkeyisvalid(i.e.,clientchannel
            * notclosed).
            */
            // Retrievedatareadearlier
            ByteBuffer buf = (ByteBuffer) key.attachment();
            buf.flip();// Preparebufferforwriting
            SocketChannel clntChan = (SocketChannel) key.channel();
            clntChan.write(buf);
            if (!buf.hasRemaining()) {// Buffercompletelywritten?
                  // Nothingleft,sonolongerinterestedinwrites
                  key.interestOps(SelectionKey.OP_READ);
            }
            buf.compact();// Makeroomformoredatatobereadin
      }
}