Eh? Sure you can listen on port X, call to port X, and succeed. Why
does it succeed when there is apparently nobody listening on port
X?
Because at the moment you begin a connect() that
"source_address/source_port/destination_address/destination_port"
unique entity exists and is in SYN_SENT state and thus can be
connected to. Check the RFC's and various BSD implementation, they
allow it too. Better yet see Steven's TCP Illustrated Volume 2, page
956 "Handle simultaneous open or self-connect".
I see about 1 or 2 people every few months who think this is illegal,
it's not.
Later,
David S. Miller
davem@redhat.com
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