From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: any way to let host act as TCP server OR client on same
 IP/port?
Date: Wed, 13 Jul 2011 19:52:00 +0200
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References: <4E1DC83C.3020506@genband.com>
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To: Chris Friesen <chris.friesen@genband.com>
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Le mercredi 13 juillet 2011 =C3=A0 10:30 -0600, Chris Friesen a =C3=A9c=
rit :
> I've been asked an interesting question about TCP.  We have some peop=
le=20
> that want to set up a TCP socket that can listen for connections on a=
=20
> given IP/port, but also initiate connections from that same IP/port.=20
> (Only one at a time, of course.)
>=20
> The TCP state machine seems to allow this (moving from LISTEN to=20
> SYN_SENT) but it's not a normal transition.
>=20
> Is there any way to do this using the socket API?
>=20
> I thought up a hack whereby we could use NFQUEUE to detect an incomin=
g=20
> SYN and delay it while we call listen() on the socket.  Is there any=20
> better way to do this?

Could you try SO_REUSEADDR, on both listener and connect attempt ?