socket, nio socket 及nio socket框架MINA总结

nio学习：
最近花了点时间研究了一下nio，及其开源框架MINA，现把心得总结如下：
1：传统socket:阻塞式通信
每建立一个Socket连接时，同时创建一个新线程对该Socket进行单独通信（采用阻塞的方式通信）。
这种方式具有很高的响应速度，并且控制起来也很简单，在连接数较少的时候非常有效，但是如果
对每一个连接都产生一个线程的无疑是对系统资源的一种浪费，如果连接数较多将会出现资源不足的情况
example:
server code:

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 = "192.161.88.22";
String proxyPort = "2080";
System.getProperties().put("socksProxySet","true");
System.getProperties().put("socksProxyHost",proxyHost);
System.getProperties().put("socksProxyPort",proxyPort);

String host = "192.20.9.18";
int port = 1086;
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 = "199.18.24.212";
String proxyPort = "8090";
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/[e-mail]/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