Who and when to call "Agent/Mcast/Control instproc recv {type iface m}??

[Cheng Liang]

Dear all,
      A simple question, not laugh at me.
      I don't know WHEN and WHO to call "Agent/Mcast/Control
instproc recv{type iface m}" in multicast protocols in NS-2.1b5, such
as MFTP ,SRM. After I made some small changes,I met the following error.
------------------------------------------------------------------
     ns: _o210 recv  2 0: no value given for parameter "m" to "_o210"
    (Agent/Mcast/Control recv line 1)
    invoked from within
"_o210 recv  2 0"
------------------------------------------------------------------
      Anyone could provide some hints, thanx a lot in advance!
      BTW. Thanks to all in NS community who ever helped me in the
past.

Cheers
Cheng Liang