luasocket: how to use 'keepalive' ?

[Valerio Schiavoni <valerio.schiavoni@...>]

Hello,
reading the LuaSocket doc for tcp, the keepalive option reports:
"'keepalive': Setting this option to true enables the periodic
transmission of messages on a connected socket. Should the connected
party fail to respond to these messages, the connection is considered
broken and processes using the socket are notified;"

Is there an example about how processes are notified, which kind of
notifications are sent out, how to handle them, etc ?

thanks,
valerio