Question

I have been developing my first TCP/Socket based application with Apache Mina, it looks great and easy to do things. I just want to ask a question here about Mina.

The server impose an idle time of 5 second will terminate the socket connection, so we have to send periodic heartbeat (echo message / keepalive) to make sure connection is alive. Sort of keepalive mechanism.

There’s one way that we send blindly echo/heartbeat message just before every 5 seconds. I am thinking, there should be smart/intelligent way “Idle Monitor” if I am sending my business message and do not come to idle time i.e. 5 second, I should not issue heartbeat message. Heartbeat message will be sent if whole connection is idle, so that we save bandwidth and fast reading & writing on socket.

Answer 1

You can achieve it by using Keep Alive Filter (already present in mina).

Alternatively, you can achieve a smarter way of sending echo/heart beat by setting session idle timeout of client a bit smaller than idle timeout of server. For example:

For server side

NioSocketAcceptor.getSessionConfig().setIdleTime(IdleStatus.BOTH_IDLE, 5);

and for client side it would be

NioSocketConnector.getSessionConfig().setIdleTime(IdleStatus.BOTH_IDLE, 3);

Now, if there is no communication for lets say 3 seconds, a sessionIdle will be triggred at the client side ( and it will not be triggered at server side as timeout there is 5 seconds) and you can send an echo. This will keep the session alive. The echo will be sent only if the session is idle.

Note: I am assuming that at session idle, session is being closed at the server side. If it is other way around you will need to switch values of session idle timeout(e.g. 3 seconds for server and 5 seconds for client) and echo will be sent from server.