socket programming

nilu511 · 08-28-2009, 01:30 AM

Hi all,
I have to run a client and server socket program in Java. When the server is up the client gets connected and my application works fine. In some condition when the server is down, the client needs to connect then it fails. For that scenario I need to run a daemon that tries to connect to the server for about 3 times before it finally throws an exception.

How should i proceed with this?

Wim Sturkenboom · 08-28-2009, 03:39 AM

Why a daemon; can't the client itself attempt three times ?

dwhitney67 · 08-28-2009, 11:08 AM

Quote:

Originally Posted by nilu511

Hi all,
I have to run a client and server socket program in Java. When the server is up the client gets connected and my application works fine. In some condition when the server is down, the client needs to connect then it fails. For that scenario I need to run a daemon that tries to connect to the server for about 3 times before it finally throws an exception.

How should i proceed with this?

As noted earlier, why do you require a daemon? Just have the client attempt to connect to the server. If it cannot connect after N-tries, then the client should exit gracefully.

Consider something like:

Code:

Socket sock = new Socket();
InetSocketAddress addr = new InetSocketAddress(host, port);

for (int i = 0; i < 3; ++i) {
   try {
      sock.connect(addr);
      break;
   }
   catch (IOException e) {
      // error
   }
}

if (sock.isConnected()) {
   // ok
}
else {
   // error
}

nilu511 · 09-01-2009, 12:41 AM

Thank you for the help and i was able to solve the problem.

nilu511 · 09-05-2009, 08:40 AM

I had a small doubt again. The solution that is suggested does not hold good in case when the client is running and the server goes down. Instead of exiting, the client should check three times whether the server has come up.
Pls suggest.

ta0kira · 09-05-2009, 11:39 AM

I'm not up on the specifics of sockets in Java, but I know how they work in general. What I'd do is have a pair of loops like this (based on dwhitney67's post):

Code:

Socket sock = new Socket();
InetSocketAddress addr = new InetSocketAddress(host, port);

while (!sock.isConnected()) {
   for (int i = 0; i < 3;) {
      try {
         sock.connect(addr);
         break;
      }
      catch (IOException e) {
         if (++i < 3) Thread.sleep(5000);
         continue;
      }
   }

   if (!sock.isConnected()) {
      break;
   }

   while (/*read or write socket*/) {
      // do stuff
   }
}

try {
   sock.close();
}

catch (IOException e) {
}

//exit routines...

This way when the inner while loop exits, the big loop will attempt to reconnect if the socket is no longer connected. Otherwise, it's assumed that the loop exit was proactive and that the client has chosen to terminate the connection. This will happen as many times as the server disconnects the client and it can reconnect within 3 tries.
Kevin Barry