How would I put my socket in non-blocking mode?
From Andrew Gierth (email@example.com):
Technically, fcntl(soc, F_SETFL, O_NONBLOCK) is incorrect since it
clobbers all other file flags. Generally one gets away with it since
the other flags (O_APPEND for example) don't really apply much to
sockets. In a similarly rough vein, you would use fcntl(soc, F_SETFL,
0) to go back to blocking mode.
To do it right, use F_GETFL to get the current flags, set or clear the
O_NONBLOCK flag, then use F_SETFL to set the flags.
And yes, the flag can be changed either way at will.