The discard protocol allows a client to send arbitrary data to a server. The data is then silently dropped.
The discard protocol is one of the first protocols implemented atop TCP and UDP; it is described in RFC 863.
No example is needed, since the protocol accepts any data and does not reply.
No discard dissector exists; it would only mark the packet as a discard protocol packet in the summary.
Example capture file
XXX - Add a simple example capture file to the SampleCaptures page and link from here (see below). Keep this file short, it's also a good idea to gzip it to make it even smaller, as Wireshark can open gzipped files automatically.
A complete list of Discard display filter fields can be found in the display filter reference
Show only the discard based traffic:
You cannot directly filter discard while capturing. However, if you know the TCP port used (see above), you can filter on that one.
Capture only the discard traffic over the default port (9):
tcp port 9
RFC 863 Discard Protocol - specification of the discard protocol.