["Guy Harris" <gharris@xxxxxxxxx>]

Larry Westrick said:
> How do I capture tcp messages between applications on the same machine
> that are using a loopback adapter or the same NIC.

The first thing to do is to make sure that the machine in question is
running Linux, one of the BSDs (including Mac OS X), or Digital/Tru64
UNIX, as those are the only OSes on which capturing on loopback adapters
is supported (note that "the same NIC" won't actually be used for sending
packets between processes on the same machine - the packet will be looped
back internally in some fashion).  If it's not, you *can't* capture
messages between applications on the same machine.

Once you've done that, you capture on the loopback interface, which will
probably have a name like "lo0" or "lo".