基于socket的心跳长连接

案例： 
心跳： 
socket模拟网页的报文连接某个网站，创建tcp的socket后，当我socket.connect后，如果在5到7秒钟不socket.send，那么这个链接就失效了。 请问如何长时间的保持这个链接 
这是在服务器端的设置的，客户端没法设置,可以发送心跳包。 
socket.connect后，每3-4秒用socket.send发送一字节数据（内容随便），然后观查这个连接是否保持。 

lientSocket=serverSocket.accept(); 
OutputStream os = clientSocket.getOutputStream();           
ObjectOutputStream oos=new ObjectOutputStream(os); 
oos.writeObject(al); 
oos.flush(); 
oos.close()//socket会关闭 

实现： 
长连接的维持，是要客户端程序，定时向服务端程序，发送一个维持连接包的。 
如果，长时间未发送维持连接包，服务端程序将断开连接。 

客户端： 
通过持有Client对象，可以随时（使用sendObject方法）发送Object给服务端。 
如果keepAliveDelay毫秒（程序中是2秒）内未发送任何数据，则，自动发送一个KeepAlive对象给服务端， 
用于维持连接。 
由于，我们向服务端，可以发送很多不同的对象，服务端也可以返回不同的对象。 
所以，对于返回对象的处理，要编写具体的ObjectAction实现类进行处理。 
通过Client.addActionMap方法进行添加。这样，程序会回调处理。 

服务端： 
由于客户端会定时（keepAliveDelay毫秒）发送维持连接的信息过来，所以，服务端要有一个检测机制。 
即当服务端receiveTimeDelay毫秒（程序中是3秒）内未接收任何数据，则，自动断开与客户端的连接。 
ActionMapping的原理与客户端相似（相同）。 
通过添加相应的ObjectAction实现类，可以实现不同对象的响应、应答过程。 

 package houlei.csdn.keepalive;

 import java.io.Serializable;
 import java.text.SimpleDateFormat;
 import java.util.Date;

 /**
  * 维持连接的消息对象。
  */
 public class KeepAlive implements Serializable{

     private static final long serialVersionUID = -2813120366138988480L;

     /* 覆盖该方法，仅用于测试使用。
      * @see java.lang.Object#toString()
      */
     @Override
     public String toString() {
         return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date())+"\t维持连接包";
     }

 }

client: 

 package houlei.csdn.keepalive;

 import java.io.IOException;
 import java.io.InputStream;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.net.Socket;
 import java.net.UnknownHostException;
 import java.util.concurrent.ConcurrentHashMap;

 /**
  *  C/S架构的客户端对象，持有该对象，可以随时向服务端发送消息。
  */
 public class Client {

     /**
      * 处理服务端发回的对象，可实现该接口。
      */
     public static interface ObjectAction{
         void doAction(Object obj,Client client);
     }
     public static final class DefaultObjectAction implements ObjectAction{
         public void doAction(Object obj,Client client) {
             System.out.println("处理：\t"+obj.toString());
         }
     }
     public static void main(String[] args) throws UnknownHostException, IOException {
         String serverIp = "127.0.0.1";
         int port = 65432;
         Client client = new Client(serverIp,port);
         client.start();
     }

     private String serverIp;
     private int port;
     private Socket socket;
     private boolean running=false;
     private long lastSendTime;
     private ConcurrentHashMap<Class, ObjectAction> actionMapping = new ConcurrentHashMap<Class,ObjectAction>();

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

     public void start() throws UnknownHostException, IOException {
         if(running)return;
         socket = new Socket(serverIp,port);
         System.out.println("本地端口："+socket.getLocalPort());
         lastSendTime=System.currentTimeMillis();
         running=true;
         new Thread(new KeepAliveWatchDog()).start();
         new Thread(new ReceiveWatchDog()).start();
     }

     public void stop(){
         if(running)running=false;
     }

     /**
      * 添加接收对象的处理对象。
      * @param cls 待处理的对象，其所属的类。
      * @param action 处理过程对象。
      */
     public void addActionMap(Class<Object> cls,ObjectAction action){
         actionMapping.put(cls, action);
     }

     public void sendObject(Object obj) throws IOException {
         ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
         oos.writeObject(obj);
         System.out.println("发送：\t"+obj);
         oos.flush();
     }

     class KeepAliveWatchDog implements Runnable{
         long checkDelay = 10;
         long keepAliveDelay = 2000;
         public void run() {
             while(running){
                 if(System.currentTimeMillis()-lastSendTime>keepAliveDelay){
                     try {
                         Client.this.sendObject(new KeepAlive());
                     } catch (IOException e) {
                         e.printStackTrace();
                         Client.this.stop();
                     }
                     lastSendTime = System.currentTimeMillis();
                 }else{
                     try {
                         Thread.sleep(checkDelay);
                     } catch (InterruptedException e) {
                         e.printStackTrace();
                         Client.this.stop();
                     }
                 }
             }
         }
     }

     class ReceiveWatchDog implements Runnable{
         public void run() {
             while(running){
                 try {
                     InputStream in = socket.getInputStream();
                     if(in.available()>0){
                         ObjectInputStream ois = new ObjectInputStream(in);
                         Object obj = ois.readObject();
                         System.out.println("接收：\t"+obj);
                         ObjectAction oa = actionMapping.get(obj.getClass());
                         oa = oa==null?new DefaultObjectAction():oa;
                         oa.doAction(obj, Client.this);
                     }else{
                         Thread.sleep(10);
                     }
                 } catch (Exception e) {
                     e.printStackTrace();
                     Client.this.stop();
                 }
             }
         }
     }

 }

server: 

 package houlei.csdn.keepalive;


 import java.io.IOException;
 import java.io.InputStream;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.concurrent.ConcurrentHashMap;

 /**
  * C/S架构的服务端对象。
  */
 public class Server {

     /**
      * 要处理客户端发来的对象，并返回一个对象，可实现该接口。
      */
     public interface ObjectAction{
         Object doAction(Object rev);
     }

     public static final class DefaultObjectAction implements ObjectAction{
         public Object doAction(Object rev) {
             System.out.println("处理并返回："+rev);
             return rev;
         }
     }

     public static void main(String[] args) {
         int port = 65432;
         Server server = new Server(port);
         server.start();
     }

     private int port;
     private volatile boolean running=false;
     private long receiveTimeDelay=3000;
     private ConcurrentHashMap<Class, ObjectAction> actionMapping = new ConcurrentHashMap<Class,ObjectAction>();
     private Thread connWatchDog;

     public Server(int port) {
         this.port = port;
     }

     public void start(){
         if(running)return;
         running=true;
         connWatchDog = new Thread(new ConnWatchDog());
         connWatchDog.start();
     }

     @SuppressWarnings("deprecation")
     public void stop(){
         if(running)running=false;
         if(connWatchDog!=null)connWatchDog.stop();
     }

     public void addActionMap(Class<Object> cls,ObjectAction action){
         actionMapping.put(cls, action);
     }

     class ConnWatchDog implements Runnable{
         public void run(){
             try {
                 ServerSocket ss = new ServerSocket(port,5);
                 while(running){
                     Socket s = ss.accept();
                     new Thread(new SocketAction(s)).start();
                 }
             } catch (IOException e) {
                 e.printStackTrace();
                 Server.this.stop();
             }

         }
     }

     class SocketAction implements Runnable{
         Socket s;
         boolean run=true;
         long lastReceiveTime = System.currentTimeMillis();
         public SocketAction(Socket s) {
             this.s = s;
         }
         public void run() {
             while(running && run){
                 if(System.currentTimeMillis()-lastReceiveTime>receiveTimeDelay){
                     overThis();
                 }else{
                     try {
                         InputStream in = s.getInputStream();
                         if(in.available()>0){
                             ObjectInputStream ois = new ObjectInputStream(in);
                             Object obj = ois.readObject();
                             lastReceiveTime = System.currentTimeMillis();
                             System.out.println("接收：\t"+obj);
                             ObjectAction oa = actionMapping.get(obj.getClass());
                             oa = oa==null?new DefaultObjectAction():oa;
                             Object out = oa.doAction(obj);
                             if(out!=null){
                                 ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());
                                 oos.writeObject(out);
                                 oos.flush();
                             }
                         }else{
                             Thread.sleep(10);
                         }
                     } catch (Exception e) {
                         e.printStackTrace();
                         overThis();
                     }
                 }
             }
         }

         private void overThis() {
             if(run)run=false;
             if(s!=null){
                 try {
                     s.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             System.out.println("关闭："+s.getRemoteSocketAddress());
         }

     }

 }