[Guy Harris <guy@xxxxxxxxxx>]

> > now i wonder how i can register a protocoll if there is no standard port
> > associated to it. or it is not using this standard port at the moment.
> 
> Unfortunately we do not have a way yet. We are close, though.
> We have the ability for protocol dissectors register the fact that they
> need to be called in certain situatoins (tcp port number, for example).

That might be sufficient in some cases, e.g. if two machines use
protocol X, running on some standard port, to set up a subsequent
conversation using protocol Y, running on some port agreed to by the
machines as part of the protocol X dialog, so that the protocol X
dissector could then use "dissector_add()" to specify that the port in
question should be used for protocol Y.

Some streaming media protocol do this, I think, for example.

In addition, 0.8.7 includes a mechanism by which a dissector can specify
that a particular TCP or UDP conversation, in the sense of "traffic
between machine A/port X and machine B/port Y", should be dissected with
some particular protocol's dissector.

However, as you note, if there's no way for Ethereal to know that port A
should be used for protocol Y, or for conversation Z, other than the
user telling it so, there's currently no mechanism for doing that.