What exactly does SO_KEEPALIVE do?
Unix Socket FAQ for Network programming
(Continued from previous question...)
What exactly does SO_KEEPALIVE do?
The SO_KEEPALIVE option causes a packet (called a 'keepalive probe')
to be sent to the remote system if a long time (by default, more than
2 hours) passes with no other data being sent or received. This packet
is designed to provoke an ACK response from the peer. This enables
detection of a peer which has become unreachable (e.g. powered off or
disconnected from the net).
Note that the figure of 2 hours comes from RFC1122, "Requirements for
Internet Hosts". The precise value should be configurable, but I've
often found this to be difficult. The only implementation I know of
that allows the keepalive interval to be set per-connection is SVR4.2.
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