用JAVA实现一个简单地Socket服务器，可以实现发给指定对象

要实现发给指定Scoket对象的重点就是将信息接受对象的socket在服务器中记录下了，这里穿个简单例子，希望大家一起完善。

EchoServer.java

package thread2;

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.net.*;
import java.util.*;

import net.sf.json.JSONObject;

public class EchoServer {
	private Selector selector = null;
	private ServerSocketChannel serverSocketChannel = null;
	private int port = 8000;
	private Charset charset = Charset.forName("UTF-8");

	private Map<String, SocketChannel> serverSocketMap;//记录socket的键值对

	public EchoServer() throws IOException {

		serverSocketMap = new HashMap<String, SocketChannel>();

		selector = Selector.open();
		serverSocketChannel = ServerSocketChannel.open();
		serverSocketChannel.socket().setReuseAddress(true);
		serverSocketChannel.socket().bind(new InetSocketAddress(port));
		System.out.println("Start");
	}

	public void accept() {
		for (;;) {
			try {
				SocketChannel socketChannel = serverSocketChannel.accept();

				System.out.println("recive client:"
						+ socketChannel.socket().getInetAddress() + ":"
						+ socketChannel.socket().getPort());
				socketChannel.configureBlocking(false);

				ByteBuffer buffer = ByteBuffer.allocate(1024);
				synchronized (gate) {
					selector.wakeup();
					socketChannel.register(selector, SelectionKey.OP_READ
							| SelectionKey.OP_WRITE, buffer);
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private Object gate = new Object();

	public void service() throws IOException {
		for (;;) {
			synchronized (gate) {
			}
			int n = selector.select();

			if (n == 0)
				continue;
			Set<SelectionKey> readyKeys = selector.selectedKeys();
			Iterator it = readyKeys.iterator();
			while (it.hasNext()) {
				SelectionKey key = null;
				try {
					key = (SelectionKey) it.next();
					it.remove();
					if (key.isReadable()) {

						receive(key);
					}
					if (key.isWritable()) {

						send(key);
					}
				} catch (IOException e) {
					e.printStackTrace();
					try {
						if (key != null) {
							key.cancel();
							key.channel().close();
						}
					} catch (Exception ex) {
						e.printStackTrace();
					}
				}
			}// #while
		}// #while
	}

	public void send(SelectionKey key) throws IOException {

		ByteBuffer buffer = (ByteBuffer) key.attachment();
		SocketChannel socketChannel = (SocketChannel) key.channel();

		buffer.flip();
		String data = decode(buffer);
		if (data.indexOf("\n") == -1)
			return;

		String outputData = data.substring(0, data.indexOf("\n") + 1);

		System.out.println("outputData =" + outputData);

		JSONObject jsonObject = JSONObject.fromObject(outputData);
		String nameString = jsonObject.getString("sender");
		System.out.println(nameString);

		/*这里实现了，要发给哪个socket*/
		if (serverSocketMap.get(nameString) == null) {

			serverSocketMap.put(nameString, socketChannel);
			
			System.out.println(nameString + "--socket save");
		}
		
		String toName = jsonObject.getString("reciver");
		
		
		if (serverSocketMap.get(toName) != null) {
			socketChannel = serverSocketMap.get(toName);
			
			String contentString = jsonObject.getString("content");
			System.out.println("contentString" + contentString);
			ByteBuffer outputBuffer = encode(outputData);

			while (outputBuffer.hasRemaining()) {
				socketChannel.write(outputBuffer);
			}
			
		}
//		/*-------------------------测试用--------------------------*/
//		String contentString = jsonObject.getString("content");
//		ByteBuffer outputBuffer = encode("echo:" + contentString);
//
//		while (outputBuffer.hasRemaining()) {
//			socketChannel.write(outputBuffer);
//		}
		
		
		
		
		ByteBuffer temp = encode(outputData);
		buffer.position(temp.limit());
		buffer.compact();
		

		if (outputData.equals("bye\r\n")) {
			key.cancel();
			socketChannel.close();
			System.out.println("断开");
		}
	}

	public void receive(SelectionKey key) throws IOException {

		ByteBuffer buffer = (ByteBuffer) key.attachment();

		SocketChannel socketChannel = (SocketChannel) key.channel();
		ByteBuffer readBuff = ByteBuffer.allocate(32);
		socketChannel.read(readBuff);
		readBuff.flip();

		buffer.limit(buffer.capacity());
		buffer.put(readBuff);

	}

	public String decode(ByteBuffer buffer) {
		CharBuffer charBuffer = charset.decode(buffer);
		return charBuffer.toString();
	}

	public ByteBuffer encode(String str) {
		return charset.encode(str);
	}

	public static void main(String args[]) throws Exception {
		final EchoServer server = new EchoServer();
		Thread accept = new Thread() {
			public void run() {
				server.accept();
			}
		};
		accept.start();
		server.service();
	}
}