This function sets the socket option requested.
The function returns undefined if there is an error.
if you don't want to pass an argument.
A common option to set on a socket is
to get around the problem
of not being able to bind to a particular address while the previous TCP
connection on that port is still making up its mind to shut down. That
would look like this:
, SOL_SOCKET, SO_REUSEADDR, 1)
or warn "Can't do setsockopt: $!\n";