Wireshark · Wireshark-dev: [Wireshark-dev] Is it possible to write a dissector for an asymmetrical protocol?

[Bob Doolittle <Robert.Doolittle@xxxxxxx>]

Hi,

I'm writing my first protocol dissector (a plugin).
I have the basics up and running.  However,
this protocol has a couple of unique issues:

1 Although encapsulated in UDP, it doesn't use a
  well-known port.  I'm OK with telling wireshark
  to decode using the protocol specifically (right-click
  on packet and select "Decode As"), and that's
  working for me at a gross level.  Now I want to
  decode the details...
2 The protocol is asymmetrical.  Packets sent by client
  and server have different formats, only distinguished
  by whether the sender is client or server.  There is
  a common header that I'll want to share decoding for,
  but after that the packet structures differ.

Is it possible to write a dissector for such a protocol?

Say I select a particular packet and choose "Decode As",
and require that the packet chosen be one sent by the server,
for instance.  Now I know what UDP port and IP address
identify the server and ditto for the client.  Can I
now build separate proto trees depending on which is
sending the packet?

Is there some other approach someone can recommend?

Thanks for any and all tips!

-Bob