keepalive timer?

[Peter Lund]

Reading the documentation for module inet:

{keepalive, Boolean}
    (TCP/IP sockets) Enables periodic transmission on a connected
    socket, when no other data is being exchanged. If the other
    end does not respond, the connection is considered broken and
    an error message will be sent to the controlling process.
    Default disabled.

My question is: How long is this period by default between checks
that the TCP connection still is alive?

Is there a way to modify the default? (I saw some traces after some
other undocumented option 'send_timeout', but I do not know if that
was relevant to this problem or not.)

-- 
Peter Lund
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http://www.lundata.se