Multicast test tools "msend", "mlisten", Andrew Daviel, TRIUMF, Jan 2003
(advax@triumf.ca)

I wanted something really simple that generated a small amount of data, which 
would not overwhelm network logging systems (the human component of them, anyhow).

Msend, Mlisten may be used to help diagnose IGMP, PIM and routing problems.

Mlisten listens on a given multicast group and port, and prints
the byte count. It also prints the ASCII content of the packet (the quiet
version "mlistenq" does not)

Msend sends packets once a second on a given multicast group and port, with
a given TTL. The default packet content is the name of the machine with the
packet count

E.g.

Send:
andrew.triumf.ca: 1845
andrew.triumf.ca: 1846
andrew.triumf.ca: 1847

Listen:
receiver got 19 bytes: www.triumf.ca: 30
receiver got 19 bytes: www.triumf.ca: 31
receiver got 19 bytes: www.triumf.ca: 32

If a 4th parameter is given to msend, it is used as data instead of a packet count, e.g.

$ msend  233.1.15.175 12345 4 hello

$ mlisten 233.1.15.175 12345
receiver got 23 bytes: www.triumf.ca: hello

It is possible to have multiple senders and receivers on the same group, in
which case mlisten will display each packet with the sender's hostname


msend, mlisten are based on uicimultsender, uicimultreceiver 
from http://vip.cs.utsa.edu/classes/cs6593s99/assignment4.html

mlisten.pl, msend.pl are Perl workalikes that may be easier to adapt for other
uses. They require use IO::Socket::Multicast from CPAN.

Multicast packets may also be sent with a TTL of 1 using netcat; e.g.

$ nc -u 233.1.15.175 12345
hello world
^C 
  

 ----
Later ..
Msend, mlisten  seem similar to Jim Gemmell's mping.exe  at  
http://research.microsoft.com/barc/mbone/mping.aspx
which combines the functions of msend and mlisten in one program.
They will interoperate to some extent.