On Wed, 7 Nov 2007, Jamie Lokier wrote:

> SO_KEEPALIVE defaults to every 2 hours, which is a bit long to keep
> open a NAT connection in my experience.
>
> You can reduce the time on some OSes using some more socket options:
>
> TCP_KEEPCNT, TCP_KEEPIDLE, TCP_KEEPINTVL.
>
> This is much better then sending data, for keeping a NAT open.

Yes, given all the facts in the case I really think SO_KEEPALIVE on the
control connection is the only near-sensible thing to do to hold
NATs/firewalls "happy". Then of course adjusting the time to a user-provided
timeout value would need to be done.

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