How to keep socket alive?

How to ensure or keep socket alive?

• Well this is a really open question here "How to ensure or keep socket alive?" I'm afraid that I have to say "sorry" for this open question. But I still wanna ask some ideas. How to provide an end-to-end solution for application, which make application know that both ends works with limited resource? Any solution or suggestion is well appreciated here.

• Answer:

  I assume you mean a TCP socket. You can't guarantee that it's alive at any given time. If enabling SO_KEEPALIVE does not do what you want, you'll need to do custom keepalive packets within the application protocol. Some protocols, for isntance, have a "NOOP" command which can be used. Under Linux (but not necessarily other OSs) you can modify the keepalive interval used by SO_KEEPALIVE on a per-socket basis (see man 7 tcp)