Help in keeping a Persistent Socket connection

Hello All,
Pardon me, this is a silly question.. I have a Client who is using socket connection to connect to a server.. Currently the client is not maintaining a persistent connection. IT connects to t he server ,sends & receives messages from the server and then closes the connection. How do I keep the Socket connection alive so I can get the messages sent from the server asynchronously ???
thanks for your time

Thanks for your reply. Can I use thread to keep the connection alive.??? If so , It would be really helpful if U can show me a sample code......
Below is my piece of code...
try{
socket_Client = new Socket(name_server,portNumber);
InputStream input = socket_Client.getInputStream();
InputStreamReader in2 = new InputStreamReader(input);
BufferedReader in = new BufferedReader(in2);
getMessages(in); //this method gets the messages from the server
} catch ( Exception e)
} finally {
socket_Client.close()
thanks again

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Urgent --- Persistent socket connection?

Hi, I have a question about the persistency of a Java Socket connection. Is it a valid idea to keep a java socket open for a long time? If so, what special care do I need to take?
My Java TCP/IP client runs as a NT service. It keeps getting input messages every few seconds, then send it thru a socket connection to a TCP/IP server. In order to avoid the overhead of opening and closing the socket every time the client gets a message to send, I want to keep the socket connection open and reuse it.
I was able to send hundreds of messages thru this way, then after a while, for no apparent reason,
the socket stops working, I typically get an exception like this:
java.net.SocketException: Connection Shutdown: JVM_recv in socket input stream read
at java.net.SocketInputStream.socketRead(Native Method)
at java.net.SocketInputStream.read (SocketInputStream.java:90)
at java.net.SocketInputStream.read (SocketInputStream.java:71)
at java.io.InputStreamReader.fill (InputStreamReader.java:163)
at java.io.InputStreamReader.read (InputStreamReader.java:239)
at java.io.BufferedReader.fill (BufferedReader.java:137)
at java.io.BufferedReader.readLine (BufferedReader.java, Compiled Code)
at java.io.BufferedReader.readLine (BufferedReader.java:329)
My programs runs on NT4.0, single-threaded. Any input would be greatly appreciated.

Is it a valid idea to keep a java socket open for a long time? If so, what
special care do I need to take?Depends.
First why keep it open? Your messages only arrive every couple of seconds, does opening/closing the connection take longer than that?
If you must then the complication you must deal with is that your code must deal with re-establishing the connection when it does fail. Opening/closing it every time avoids that issue. The connection will fail, because computers fail, networks fail and people make mistakes. Which doesn't mean that you shouldn't but merely that you should consider the implications of why you need to keep it open.

Persistent socket connection - socket write error

I'm connecting to a server using sockets. My application acts like a client, sending requests, and also like a server, listenning for notifications. I was using a client socket for the first task (send a message when required) and a server socket for the second (permanently listen for incoming messages). This needs to be some kind of persistent connection.
It happens now I'm required to send and receive using the same port. The only way I found to do this is to have a single socket (client) bound to a certain port. It connects to the server and one thread keeps listenning for incoming messages (by reading the input stream) while another process is launched whenever I need to send a message (by writing to the socket's output stream). The socket is created only once (when the application starts) and its output/input streams reused whenever needed.
This works well for a while. However, when I try to send a message after some idle time (lets say 20 minutes) strange things happen. The first attempt to send a message returns success (although nothing is actually received by the server). The second attempt returns java.net.SocketException: Software caused connection abort: socket write error. I don't understand this behaviour. Can there be a timeout? I only write to the socket after testing if it's connected.. So why is this failing? Also, any other ideas on how to send and receive using the same port? A different and better approach maybe..
Thanks in advance

Socket.isConnected just tells you whether you have personally called Socket.connect() or new Socket(host, port,...). It doesn't tell you anything about the state of the connection.
You should certainly issue periodic application 'pings' at suitable intervals, and many application protocols do this. For example, Java RMI reuses connections that are less than 15 seconds old but only if they pass a ping test.
In general however you can't insist on a persistent connection over TCP/IP, especially if you have this kind of hardware in the circuit. What you can do is recognize when the connection has been lost and form a new one. The network is going to fail somewhere some time and your program has to be robust against that.

Persistent Socket Connection

Hi
We have implemented a composite, where we are connecting to a systm using socket adapter. After moving to production we realize that our application is sending CLOSE_WAIT signal in the socket in predetermined interval, but the client application is not able to close the socket immediately. They are saying that their application is tuned to work with dedicated TCP/IP connections.
We were wondering if there any way to setup dedicated connections, i.e., not to close the socket. We have turned on the keep-alive parameter in socket adapter. We are looking some option at OS level (Sloaris in our case) like tcp_time_wait_interval. But I think this will impact globally which we don't want for obvious reasons.
Regards

Hi All,
Interesting result. After we have turned off keepAlive property, we can see the number CLOSE_WAIT sockets have reduced (almost zero), and now we can see TIME_WAIT sockets for sometime, which is okay.
I guess the back end application had some problem with socket timeout settings.
Regards

Keep opened socket connection?

Hi,
My Java application communicates with server on average every 3 seconds. I wonder if it is a good idea to keep an opened socket connection to the server and don't open new connection for each request. The problem with this is that if in the meantime is connection aborted, java.net.SocketException is throwned.
What do you think about keeping opened connection? Is appropriate to work with opened connections or to open new connection for each new request? How do you solve in your applications situation when communication is irregular but frequent.
Thanks.

I had one more question on this topic relating to capture and processing exceptions. Communication between client and server I accomplish wit these three classes:
- ClientRequest - represents client request to the server
- Communication - gets ClientRequest and socket connection to the server and sends the request to the server
- ServerResponse - represents response returned from the server
Now If Communication class gets dead connection it can't work and throws an exception. We discussed that I should find out the situation and suitably respond to this situation.
My question is whether the method for reconnection should call:
a) Communication class
b) class that uses the Communication class?
c) somebody else (?)
In case a) there is an advantage that all is in one place and Communication class user does not have to worry about anything beause class will try reconnect itself (if second attempt fails, method throws another exception). The advantage of b) is that the user needs, he can respond to this situation and do some another action.
Thanks.

Is it wise to keep the socket connection open?

When u have a bunch of HTTP requests coming in to a listener server socket, would it be safe to keep my JAVA socket connection open with KeepAlive or simply open/close at will? I thought of a connection of sockets as well. Thoughts? thx!

It depends which socket your talking about
The serversocket you want to always be open and listened to
the sockets it spawns you should close when you've finished the transaction

Servlets or EJB for Persistent external socket connections

We have a Servlet that establishes a socket connection to another
external server and sends and receives messages. We have the Servlet defined as pre-loaded when JRun starts.
When JRun is started, the Servlet is started and connection is
established with the external server. The problem is when a new message is being sent, the Servlet is instantiate again and the connection is stopped and restarted. We do a forward request from another Servlet to this.
Am I totally misunderstanding Servlets because reading articles
and books seems to indicate that I should create an EJB instead of a
Servlet if you want a persistent connection.
Thanks in advance for your help.

I assume then that your connection to the external server is achieved in the "init" method of your servlet. Therefore every time the servlet container is called upon to accesss your servlet, it instantiates it - thus a new connection will be being made each time.
I would take out the connection properties from the init method. I.e. you only want it to happen once.
T

I suppose it is the problem with socket connection,Please help

Hi,
I'm trying to build a chat server in Java on Linux OS.I've created basically 2 classes in the client program.The first one shows the login window.When we enter the Login ID & password & click on the ok button,the data is sent to the server for verification.If the login is true,the second class is invoked,which displays the messenger window.This class again access the server
for collecting the IDs of the online persons.But this statement which reads from the server causes an exception in the program.If we invoke the second class independently(ie not from 1st class) then there is no problem & the required data is read from the server.Can anyone please help me in getting this program right.I'm working on a p4 machine with JDK1.4.
The Exceptions caused are given below
java.net.SocketException: Connection reset by peer: Connection reset by peer
at java.net.SocketInputStream.SocketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:119)
     at java.io.InputStreamReader$CharsetFiller.readBytes(InputStreanReader.java :339)
     at java.io.InputStreamReader$CharsetFiller.fill(InputStreamReader.java:374)
     at java.io.InputStreamReader.read(InputStreamReader.java:511)
     at java.io.BufferedReader.fill(BufferedReader.java:139)
     at java.io.BufferedReader.readLine(BufferedReader.java:299)
     at java.io.BufferedReader.readLine(BufferedReader.java:362)
     at Login.LoginData(Login.java:330)
     at Login.test(Login.java:155)
     at Login$Buttonhandler.actionPerformed(Login.java:138)
     at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1722)
     at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:17775)
     at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:4141)
     at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:253)
     at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:261)
     at java.awt.Component.processMouseEvent(Component.java:4906)
     at java.awt.Component.processEvent(component.java:4732)
     at java.awt.Container.processEvent(Container.java:1337)
     at java.awt.component.dispatchEventImpl(Component.java:3476)
     at java.awt.Container.dispatchEventImpl(Container.java:1399)
     at java.awt.Component.dispatchEvent(Component.java:3343)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3302)
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3014)
     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2967)
     at java.awt.Container.dispatchEventImpl(Container.java:1373)
     at java.awt.window.dispatchEventImpl(Window.java:1459)
     at java.awt.Component.dispatchEvent(Component.java:3343)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:439)
     at java.awt.EventDispatchThread.pumpOneEvent(EventDispatchThread.java:150)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:131)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)
     My program looks somewhat like this :
1st class definition:
public class Login extends Jframe// Login is the name of the first class;
Socket connection;
DataOutputStream outStream;
BufferedReader inStream;
Frame is set up here
public class Buttonhandler implements ActionListener
public void actionPerformed(ActionEvent e) {
String comm = e.getActionCommand();
if(comm.equals("ok")) {
check=LoginCheck(ID,paswd);
test();
public void test() //checks whether the login is true
if(check)
new Messenger(ID);// the second class is invoked
public boolean LoginCheck(String user,String passwd)
//Enter the Server's IP & port below
String destination="localhost";
int port=1234;
try
connection=new Socket(destination,port);
}catch (UnknownHostException ex){
error("Unknown host");
catch (IOException ex){
ex.printStackTrace ();
error("IO error creating socket ");
try{
inStream = new BufferedReader(new InputStreamReader(connection.getInputStream()));
outStream=new DataOutputStream(connection.getOutputStream());
}catch (IOException ex){
error("IO error getting streams");
ex.printStackTrace();
System.out.println("connected to "+destination+" at port "+port+".");
BufferedReader keyboardInput=new BufferedReader(new InputStreamReader(System.in));
String receive=new String();
try{
receive=inStream.readLine();
}catch(IOException ex){ error("Error reading from server");}
if(receive.equals("Logintrue"))
check=true;
else
check=false;
try{
inStream.close();
outStream.close();
connection.close();
}catch (IOException ex){
error("IO error closing socket");
return(check);
// second class is defined below
public class Messenger
Socket connect;
DataOutputStream outStr;
BufferedReader inStr;
public static void main(String args[])
{ Messenger mes = new Messenger(args[0]);}
Messenger(String strg)
CreateWindow();
setupEvents();
LoginData(strg);
fram.show();
void setupEvents()
fram.addWindowListener(new WindowHandler());
login.addActionListener(new MenuItemHandler());
quit.addActionListener(new MenuItemHandler());
button.addActionListener(new Buttonhandle());
public void LoginData(String name)
//Enter the Server's IP & port below
String dest="localhost";
int port=1234;
int r=0;
String str[]=new String[40];
try
connect=new Socket(dest,port);
}catch (UnknownHostException ex){
error("Unknown host");
catch (IOException ex){
ex.printStackTrace ();
error("IO error creating socket ");
try{
inStr = new BufferedReader(new InputStreamReader(connect.getInputStream()));
outStr=new DataOutputStream(connect.getOutputStream());
}catch (IOException ex){
error("IO error getting streams");
ex.printStackTrace();
String codeln=new String("\n");
try{
outStr.flush();
outStr.writeBytes("!@*&!@#$%^");//code for sending logged in users
outStr.writeBytes(codeln);
outStr.write(13);
outStr.flush();
String check="qkpltx";
String receive=new String();
try{
while((receive=inStr.readLine())!=null) //the statement that causes the exception
if(receive.equals(check))
break;
else
     str[r]=receive;
     r++;
}catch(IOException ex){ex.printStackTrace();error("Error reading from socket");}
catch(NullPointerException ex){ex.printStackTrace();}
} catch (IOException ex){ex.printStackTrace();
error("Error reading from keyboard or socket ");
try{
inStr.close();
outStr.close();
connect.close();
}catch (IOException ex){
error("IO error closing socket");
for(int l=0,k=1;l<r;l=l+2,k++)
if(!(str[l].equals(name)))
stud[k]=" "+str[l];
else
k--;
public class Buttonhandle implements ActionListener
public void actionPerformed(ActionEvent e) {
//chat with the selected user;
public class MenuItemHandler implements ActionListener
public void actionPerformed(ActionEvent e)
String cmd=e.getActionCommand();
if(cmd.equals("Disconnect"))
//Disconnect from the server
else if(cmd.equals("Change User"))
     //Disconnect from the server & call the login window
else if(cmd.equals("View Connection Details"))
//show connection details;
public class WindowHandler extends WindowAdapter
public void windowClosing(WindowEvent e){
//Disconnect from server & then exit;
System.exit(0);}
I�ll be very thankful if anyone corrects the mistake for me.Please help.

You're connecting to the server twice. After you've successfully logged in, pass the Socket to the Messenger class.
public class Messenger {
    Socket connect;
    public static void main(String args[]) {
        Messenger mes = new Messenger(args[0]);
    Messenger(Socket s, String strg) {
        this.connect = s;
        CreateWindow();
        setupEvents();
        LoginData(strg);
        fram.show();
}

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Help in keeping a Persistent Socket connection

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