[closed] how to use heur_dissector_add() function to dissect.

I have put the dissector upon "udp".But in the wireshark UI,open a packet,select a item, use the "disscetor as" option. the question is :there is no fp(my protocol) to select.why? thank U very much! follow is the code.

void proto_reg_handoff_fp(void) { mac_fdd_rach_handle = find_dissector("mac.fdd.rach"); mac_fdd_fach_handle = find_dissector("mac.fdd.fach"); mac_fdd_pch_handle = find_dissector("mac.fdd.pch"); mac_fdd_dch_handle = find_dissector("mac.fdd.dch"); mac_fdd_edch_handle = find_dissector("mac.fdd.edch"); mac_fdd_hsdsch_handle = find_dissector("mac.fdd.hsdsch"); heur_dissector_add("udp", heur_dissect_fp, proto_fp); }