JAVA实现长连接(含心跳检测Demo)

实现原理：
       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：
       Client通过持有Socket的对象，可以随时（使用sendObject方法）发送Massage Object(消息)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 Object(心跳)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消息对象，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。

Demo:

package socket.keepalive.test;

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

/**
*
* 维持连接的消息对象（心跳对象）
*/
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";
}

}

package socket.keepalive.test;

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.Collections;
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。
* <p>
* 创建时间：2010-7-18 上午12:17:25
* @author HouLei
* @since 1.0
*/
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; //连接状态

private long lastSendTime; //最后一次发送数据的时间

//用于保存接收消息对象类型及该类型消息处理的对象
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(); //保持长连接的线程，每隔2秒项服务器发一个一个保持连接的心跳消息
new Thread(new ReceiveWatchDog()).start();  //接受消息的线程，处理消息
}

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();
 }
 }
}
}

}

package socket.keepalive.test;

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。
* <p>
* 创建时间：2010-7-18 上午12:17:37
* @author HouLei
* @since 1.0
*/
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, Server server);
}

public static final class DefaultObjectAction implements ObjectAction{
public Object doAction(Object rev,Server server) {
 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,Server.this);
   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());
}

}

}

来源：https://blog.csdn.net/zmx729618/article/details/54378259