public class MultiUserServer extends Thread {
 private Socket client;
 
 public MultiUserServer(Socket c) {
  this.client = c;
 }

 public void run() {
  try {
   BufferedReader in = new BufferedReader(new InputStreamReader(client
     .getInputStream()));
   PrintWriter out = new PrintWriter(client.getOutputStream());
   // Mutil User but can't parallel
   while (true) {
    String str = in.readLine();
    System.out.println(str);
    SocketLog.debug("receive message: " + str);
    out.println("has receive....");
    out.flush();
    if (str.equals("end"))
     break;
   }
   client.close();
  } catch (IOException ex) {
  }
 }

 public static void main(String[] args) throws IOException {
  int port = 5678;
  if (args.length > 0)
   port = Integer.parseInt(args[0]);
  ServerSocket server = new ServerSocket(port);
  SocketLog.debug("the server socket application is created!");
  while (true) {
   // transfer location change Single User or Multi User
   MultiUserServer mu = new MultiUserServer(server.accept());
   mu.start();
  }
 }
}

client code:

public class Client {

 static Socket server;

 public static void main(String[] args) throws Exception {
  
  //set socket proxy.
  String proxyHost = "192.168.254.212";
  String proxyPort = "1080";
  System.getProperties().put("socksProxySet","true");
  System.getProperties().put("socksProxyHost",proxyHost);
  System.getProperties().put("socksProxyPort",proxyPort);
  
  String host = "132.201.69.80";
  int port = 13086;
  if (args.length > 1)
  {
   host = args[0];
   port = Integer.parseInt(args[1]);
  }
  System.out.println("connetioning:" + host + ":" + port);
  server = new Socket(host, port);
  BufferedReader in = new BufferedReader(new InputStreamReader(server
    .getInputStream()));
  PrintWriter out = new PrintWriter(server.getOutputStream());
  BufferedReader wt = new BufferedReader(new InputStreamReader(System.in));
  while (true) {
   String str = wt.readLine();
   out.println(str);
   out.flush();
   if (str.equals("end")) {
    break;
   }
   System.out.println(in.readLine());
  }
  server.close();
 }
}

2.nio:非阻塞通讯模式
２．１NIO 设计背后的基石：反应器模式，用于事件多路分离和分派的体系结构模式。
反应器模式的核心功能如下：
将事件多路分用
将事件分派到各自相应的事件处理程序

NIO 的非阻塞 I/O 机制是围绕 选择器和 通道构建的。 Channel 类表示服务器和客户机之间的
一种通信机制。Selector 类是 Channel 的多路复用器。 Selector 类将传入客户机请求多路分
用并将它们分派到各自的请求处理程序。
通道(Channel 类)：表示服务器和客户机之间的一种通信机制。
选择器(Selector类)：是 Channel 的多路复用器。Selector 类将传入的客户机请求多路分用并将它们
分派到各自的请求处理程序。

简单的来说：

NIO是一个基于事件的IO架构，最基本的思想就是：有事件我通知你，你再去做你的事情．
而且NIO的主线程只有一个，不像传统的模型，需要多个线程以应对客户端请求，也减轻
了JVM的工作量。
当Channel注册至Selector以后，经典的调用方法如下：

        while (somecondition) {
            int n = selector.select(TIMEOUT);
            if (n == 0)
                continue;
            for (Iterator iter = selector.selectedKeys().iterator(); iter
                    .hasNext();) {
                if (key.isAcceptable())
                    doAcceptable(key);
                if (key.isConnectable())
                    doConnectable(key);
                if (key.isValid() && key.isReadable())
                    doReadable(key);
                if (key.isValid() && key.isWritable())
                    doWritable(key);
                iter.remove();
            }
        }
nio中取得事件通知，就是在selector的select事件中完成的。在selector事件时有一个线程
向操作系统询问，selector中注册的Channel&&SelectionKey的键值对的各种事件是否有发生，
如果有则添加到selector的selectedKeys属性Set中去，并返回本次有多少个感兴趣的事情发生。
如果发现这个值>0，表示有事件发生，马上迭代selectedKeys中的SelectionKey，
根据Key中的表示的事件，来做相应的处理。
实际上，这段说明表明了异步socket的核心，即异步socket不过是将多个socket的调度（或者还有他们的线程调度）
全部交给操作系统自己去完成，异步的核心Selector，不过是将这些调度收集、分发而已。
2.2 nio example:
server code：

public class NonBlockingServer
{
    public Selector sel = null;
    public ServerSocketChannel server = null;
    public SocketChannel socket = null;
    public int port = 4900;
    String result = null;

    public NonBlockingServer()
    {
  System.out.println("Inside default ctor");
    }
   
 public NonBlockingServer(int port)
    {
  System.out.println("Inside the other ctor");
  this.port = port;
    }

    public void initializeOperations() throws IOException,UnknownHostException
    {
  System.out.println("Inside initialization");
  sel = Selector.open();
  server = ServerSocketChannel.open();
  server.configureBlocking(false);
  InetAddress ia = InetAddress.getLocalHost();
  InetSocketAddress isa = new InetSocketAddress(ia,port);
  server.socket().bind(isa);
    }
   
 public void startServer() throws IOException
    {
  System.out.println("Inside startserver");
        initializeOperations();
  System.out.println("Abt to block on select()");
  SelectionKey acceptKey = server.register(sel, SelectionKey.OP_ACCEPT ); 
 
  while (acceptKey.selector().select() > 0 )
  { 
    
   Set readyKeys = sel.selectedKeys();
   Iterator it = readyKeys.iterator();

   while (it.hasNext()) {
    SelectionKey key = (SelectionKey)it.next();
    it.remove();
               
    if (key.isAcceptable()) {
     System.out.println("Key is Acceptable");
     ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
     socket = (SocketChannel) ssc.accept();
     socket.configureBlocking(false);
     SelectionKey another = socket.register(sel,SelectionKey.OP_READ|SelectionKey.OP_WRITE);
    }
    if (key.isReadable()) {
     System.out.println("Key is readable");
     String ret = readMessage(key);
     if (ret.length() > 0) {
      writeMessage(socket,ret);
     }
    }
    if (key.isWritable()) {
     System.out.println("THe key is writable");
     String ret = readMessage(key);
     socket = (SocketChannel)key.channel();
     if (result.length() > 0 ) {
      writeMessage(socket,ret);
     }
    }
   }
  }
    }

    public void writeMessage(SocketChannel socket,String ret)
    {
  System.out.println("Inside the loop");

  if (ret.equals("quit") || ret.equals("shutdown")) {
   return;
  }
  try
  {

   String s = "This is context from server!-----------------------------------------";
   Charset set = Charset.forName("us-ascii");
   CharsetDecoder dec = set.newDecoder();
   CharBuffer charBuf = dec.decode(ByteBuffer.wrap(s.getBytes()));
   System.out.println(charBuf.toString());
   int nBytes = socket.write(ByteBuffer.wrap((charBuf.toString()).getBytes()));
   System.out.println("nBytes = "+nBytes);
    result = null;
  }
  catch(Exception e)
  {
   e.printStackTrace();
  }

    }
 
    public String readMessage(SelectionKey key)
    {
  int nBytes = 0;
  socket = (SocketChannel)key.channel();
        ByteBuffer buf = ByteBuffer.allocate(1024);
  try
  {
            nBytes = socket.read(buf);
   buf.flip();
   Charset charset = Charset.forName("us-ascii");
   CharsetDecoder decoder = charset.newDecoder();
   CharBuffer charBuffer = decoder.decode(buf);
   result = charBuffer.toString();
    
        }
  catch(IOException e)
  {
   e.printStackTrace();
  }
  return result;
    }

    public static void main(String args[])
    {
     NonBlockingServer nb;
     if (args.length < 1)
     {
      nb = new NonBlockingServer();
     }
     else
     {
      int port = Integer.parseInt(args[0]);
      nb = new NonBlockingServer(port);
     }
  
  try
  {
   nb.startServer();
   System.out.println("the nonBlocking server is started!");
  }
  catch (IOException e)
  {
   e.printStackTrace();
   System.exit(-1);
  }
  
 }
}

client code:

public class Client {
 public SocketChannel client = null;

 public InetSocketAddress isa = null;

 public RecvThread rt = null;

 private String host;

 private int port;

 public Client(String host, int port) {
  this.host = host;
  this.port = port;
 }

 public void makeConnection() {
  String proxyHost = "192.168.254.212";
  String proxyPort = "1080";
  System.getProperties().put("socksProxySet", "true");
  System.getProperties().put("socksProxyHost", proxyHost);
  System.getProperties().put("socksProxyPort", proxyPort);

  int result = 0;
  try {
   client = SocketChannel.open();
   isa = new InetSocketAddress(host, port);
   client.connect(isa);
   client.configureBlocking(false);
   receiveMessage();
  } catch (UnknownHostException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
  long begin = System.currentTimeMillis();

  sendMessage();

  long end = System.currentTimeMillis();
  long userTime = end - begin;
  System.out.println("use tiem: " + userTime);
  try {
   interruptThread();
   client.close();
   System.exit(0);
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

 public int sendMessage() {
    System.out.println("Inside SendMessage");
  String msg = null;
  ByteBuffer bytebuf;
  int nBytes = 0;
  try {
   msg = "It's message from client!";
   System.out.println("msg is "+msg);
   bytebuf = ByteBuffer.wrap(msg.getBytes());
   for (int i = 0; i < 1000; i++) {
    nBytes = client.write(bytebuf);
    System.out.println(i + " finished");
   }
   interruptThread();
   try {
    Thread.sleep(5000);
   } catch (Exception e) {
    e.printStackTrace();
   }
   client.close();
   return -1;

  } catch (IOException e) {
   e.printStackTrace();
  }

  return nBytes;

 }

 public void receiveMessage() {
  rt = new RecvThread("Receive THread", client);
  rt.start();

 }

 public void interruptThread() {
  rt.val = false;
 }

 public static void main(String args[]) {
  if (args.length < 2) {
   System.err.println("You should put 2 args: host,port");
  } else {
   String host = args[0];
   int port = Integer.parseInt(args[1]);
   Client cl = new Client(host, port);
   cl.makeConnection();
  }
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String msg;

 }

 public class RecvThread extends Thread {
  public SocketChannel sc = null;

  public boolean val = true;

  public RecvThread(String str, SocketChannel client) {
   super(str);
   sc = client;
  }

  public void run() {
   int nBytes = 0;
   ByteBuffer buf = ByteBuffer.allocate(2048);
   try {
    while (val) {
     while ((nBytes = nBytes = client.read(buf)) > 0) {
      buf.flip();
      Charset charset = Charset.forName("us-ascii");
      CharsetDecoder decoder = charset.newDecoder();
      CharBuffer charBuffer = decoder.decode(buf);
      String result = charBuffer.toString();
      System.out.println("the server return: " + result);
      buf.flip();

     }
    }

   } catch (IOException e) {
    e.printStackTrace();

   }

  }
 }
}
3：Socket网络框架 MINA
MINA是一个网络应用框架，在不牺牲性能和可扩展性的前提下用于解决如下问题：
1：快速开发自己的英勇。
2：高可维护性，高可复用性：网络I/O编码，消息的编/解码，业务逻辑互相分离。
3：相对容易的进行单元测试。

3.1 IoFilters：
IoFilter为MINA的功能扩展提供了接口。它拦截所有的IO事件进行事件的预处理和后处理(AOP)。我们可以把它想象成
Servlet的filters。
IoFilter能够实现以下几种目的：
事件日志
性能检测
数据转换(e.g. SSL support)，codec
防火墙…等等

3.2 codec: ProtocolCodecFactory
MINA提供了方便的Protocol支持。如上说讲，codec在IoFilters中设置。
通过它的Encoder和Decoder，可以方便的扩展并支持各种基于Socket的网络协议，比如HTTP服务器、FTP服务器、Telnet服务器等等。

要实现自己的编码/解码器(codec)只需要实现interface: ProtocolCodecFactory即可.
在MINA 1.0版本，MINA已经实现了几个常用的(codec factory):

DemuxingProtocolCodecFactory,
NettyCodecFactory,
ObjectSerializationCodecFactory,
TextLineCodecFactory
 
其中：
TextLineCodecFactory:
 A ProtocolCodecFactory that performs encoding and decoding between a text line data and a Java
 string object. This codec is useful especially when you work with a text-based protocols such as SMTP and IMAP.

ObjectSerializationCodecFactory:
A ProtocolCodecFactory that serializes and deserializes Java objects. This codec is very useful when
you have to prototype your application rapidly without any specific codec.

DemuxingProtocolCodecFactory：
A composite ProtocolCodecFactory that consists of multiple MessageEncoders and MessageDecoders. ProtocolEncoder
and ProtocolDecoder this factory returns demultiplex incoming messages and buffers to appropriate MessageEncoders
and MessageDecoders.

NettyCodecFactory:
A MINA ProtocolCodecFactory that provides encoder and decoder for Netty2 Messages and MessageRecognizers.

3.3 business logic: IoHandler

MINA中，所有的业务逻辑都有实现了IoHandler的class完成
interfaceHandles:
 all protocol events fired by MINA. There are 6 event handler methods, and they are all invoked by MINA automatically.
 当事件发生时，将触发IoHandler中的方法:
 sessionCreated, sessionOpened, sessionClosed, sessionIdle, exceptionCaught, messageReceived, messageSent
MINA 1.O中，IoHandler的实现类：
ChainedIoHandler, DemuxingIoHandler, IoHandlerAdapter, SingleSessionIoHandlerDelegate, StreamIoHandler
具体细节可参考javadoc。

3.4   MINA的高级主题：线程模式
MINA通过它灵活的filter机制来提供多种线程模型。
没有线程池过滤器被使用时MINA运行在一个单线程模式。
如果添加了一个IoThreadPoolFilter到IoAcceptor，将得到一个leader-follower模式的线程池。
如果再添加一个ProtocolThreadPoolFilter，server将有两个线程池；
一个(IoThreadPoolFilter)被用于对message对象进行转换，另外一个(ProtocolThreadPoolFilter)被用于处理业务逻辑。
SimpleServiceRegistry加上IoThreadPoolFilter和ProtocolThreadPoolFilter的缺省实现即可适用于需
要高伸缩性的应用。如果想使用自己的线程模型，请参考SimpleServiceRegistry的源代码，并且自己

初始化Acceptor。

IoThreadPoolFilter threadPool = new IoThreadPoolFilter();threadPool.start();
IoAcceptor acceptor = new SocketAcceptor();
acceptor.getFilterChain().addLast( "threadPool", threadPool);
ProtocolThreadPoolFilter threadPool2 = new ProtocolThreadPoolFilter();
threadPool2.start();
ProtocolAcceptor acceptor2 = new IoProtocolAcceptor( acceptor );
acceptor2.getFilterChain().addLast( "threadPool", threadPool2 );
...
threadPool2.stop();
threadPool.stop();

采用MINA进行socket开发，一般步骤如下：
1：
server:
IoAcceptor acceptor = new SocketAcceptor(); //建立client接收器
or client:
SocketConnector connector = new SocketConnector();  //建立一个连接器
2：server的属性配置：
        SocketAcceptorConfig cfg = new SocketAcceptorConfig();
        cfg.setReuseAddress(true);
        cfg.getFilterChain().addLast(
                    "codec",
                    new ProtocolCodecFilter( new ObjectSerializationCodecFactory() ) ); //对象序列化 codec factory
        cfg.getFilterChain().addLast( "logger", new LoggingFilter() );
3：绑定address和business logic
server:
        acceptor.bind(
                new InetSocketAddress( SERVER_PORT ),
                new ServerSessionHandler( ), cfg ); // 绑定address和handler

client:
        connector.connect(new InetSocketAddress( HOSTNAME, PORT ),
                        new ClientSessionHandler(msg), cfg );

下面的这个简单的example演示client和server传递object的过程：
Message.java
public class Message implements Serializable {

    private int type;
    private int status;
    private String msgBody;
   
    public Message(int type, int status, String msgBody)
    {
        this.type = type;
        this.status = status;
        this.msgBody = msgBody;
    }

    public String getMsgBody() {
        return msgBody;
    }

    public void setMsgBody(String msgBody) {
        this.msgBody = msgBody;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }
}

Client.java
public class Client
{
    private static final String HOSTNAME = "localhost";
    private static final int PORT = 8080;
    private static final int CONNECT_TIMEOUT = 30; // seconds

    public static void main( String[] args ) throws Throwable
    {
        SocketConnector connector = new SocketConnector();       
        // Configure the service.
        SocketConnectorConfig cfg = new SocketConnectorConfig();
        cfg.setConnectTimeout( CONNECT_TIMEOUT );
          cfg.getFilterChain().addLast(
                    "codec",
                    new ProtocolCodecFilter( new ObjectSerializationCodecFactory() ) );

        cfg.getFilterChain().addLast( "logger", new LoggingFilter() );
       
        IoSession session;
        Message msg = new Message(0,1,"hello");
        connector.connect(new InetSocketAddress( HOSTNAME, PORT ),
                        new ClientSessionHandler(msg), cfg );

    }
}

ClientSessionHandler.java
public class ClientSessionHandler extends IoHandlerAdapter
{
    private Object msg;
   
    public ClientSessionHandler(Object msg)
    {
        this.msg = msg;
    }

    public void sessionOpened( IoSession session )
    {
        session.write(this.msg);
    }

    public void messageReceived( IoSession session, Object message )
    {
        System.out.println("in messageReceived!");
        Message rm = (Message ) message;       
        SessionLog.debug(session, rm.getMsgBody());
        System.out.println("message is: " + rm.getMsgBody());
        session.write(rm);
    }

    public void exceptionCaught( IoSession session, Throwable cause )
    {
        session.close();
    }
}

Server.java
public class Server
{
    private static final int SERVER_PORT = 8080;

    public static void main( String[] args ) throws Throwable
    {
        IoAcceptor acceptor = new SocketAcceptor();
       
        // Prepare the service configuration.
        SocketAcceptorConfig cfg = new SocketAcceptorConfig();
        cfg.setReuseAddress( true );

        cfg.getFilterChain().addLast(
                    "codec",
                    new ProtocolCodecFilter( new ObjectSerializationCodecFactory() ) );
        cfg.getFilterChain().addLast( "logger", new LoggingFilter() );

        acceptor.bind(
                new InetSocketAddress( SERVER_PORT ),
                new ServerSessionHandler( ), cfg );

        System.out.println( "The server Listening on port " + SERVER_PORT );
    }
}

ServerSessionHandler.java
public class ServerSessionHandler extends IoHandlerAdapter
{
    public void sessionOpened( IoSession session )
    {
        // set idle time to 60 seconds
        session.setIdleTime( IdleStatus.BOTH_IDLE, 60 );
        session.setAttribute("times",new Integer(0));
    }

    public void messageReceived( IoSession session, Object message )
    {
        System.out.println("in messageReceived");
        int times = ((Integer)(session.getAttribute("times"))).intValue();
        System.out.println("tiems = " + times);
        // communicate 30 times,then close the session.
        if (times < 30)
        {
            times++;
            session.setAttribute("times", new Integer(times));          
         Message msg;
         msg = (Message) message;
         msg.setMsgBody("in server side: " + msg.getMsgBody()); 
         System.out.println("begin send msg: " + msg.getMsgBody());
         session.write(msg);
        }
        else
        {
            session.close();
        }
    }

    public void sessionIdle( IoSession session, IdleStatus status )
    {
        SessionLog.info( session, "Disconnecting the idle." );
        // disconnect an idle client
        session.close();
    }

    public void exceptionCaught( IoSession session, Throwable cause )
    {
        // close the connection on exceptional situation
        session.close();
    }
}
MINA自己附带的Demo已经很好的说明了它的运用。
值得一提的是它的SumUp：客户端发送几个数字，服务端求和后并返回结果。这个简单的程序演示了如何自己实现CODEC。

补充提示：
下载并运行MINA的demo程序还颇非周折:
运行MINA demo appli擦tion：
1:在JDK5
产生错误:
Exception in thread "main" java.lang.NoClassDefFoundError: edu/emory/mathcs/backport/java/util/concurrent/Executor
 at org.apache.mina.example.reverser.Main.main(Main.java:44)
 
察看mina的QA email:
http://www.mail-archive.com/mina-dev@directory.apache.org/msg02252.html

原来需要下载:backport-util-concurrent.jar并加入classpath
http://dcl.mathcs.emory.edu/util/backport-util-concurrent/

继续运行还是报错:
Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory

原来MINA采用了slf4j项目作为log，继续下载
slf4j-simple.jar等，并加入classpath:
http://www.slf4j.org/download.html