[CentOS] Socket behavior change from 6.5 to 6.6

Fri Jan 16 19:23:56 UTC 2015
Les Mikesell <lesmikesell at gmail.com>

On Fri, Jan 16, 2015 at 1:13 PM, Fred Smith
<fredex at fcshome.stoneham.ma.us> wrote:
>> >
>> > Normally if you care about knowing if the other end of a connection is
>> > gone you could enable keepalives on the socket
>> That’s also an appropriate fix, especially when the protocol inherently has long periods of idle time, like SSH.
> It's been some time since I've dealt with that sort of problem, but My
> recollection is that even keepalives won't really work, because they
> occur only every hour or two.

You can control the frequency - and they are sometimes useful to keep
otherwise idle connections established through firewalls and NAT
gateways that would time out and drop them.

> I suppose this kludge would work too: try sending something on that port,
> and if the connection is broken, it'll error. then you could open a new
> one.

The problem here is that if the other end isn't reading from the
socket - and a camera probably wouldn't - the writes will just queue
up until some buffer is filled.    And, without keepalives enabled,
you still won't get an error on the write.

   Les Mikesell
     lesmikesell at gmail.com