The command mentioned by colleague will only be applicable to SRX with 11.1 junos onwards..
you should be able to ping multicast ip using the command as long as you can configure SAP in edit protocols hierarchy.
However, EX4200 doesn't support this:
{master:0}[edit]
root@ex4200# show protocols sap
##
## Warning: configuration block ignored: unsupported platform (ex4200-24f)
##
listen 225.100.100.100;
{master:0}[edit]
root@ex4200#
I see that 11.4R11 on SRX100 have this:
root# show protocols sap
listen 255.100.100.100;
[edit]
root# run show version
Model: srx100b
JUNOS Software Release [11.4R11.4]
..
So you may configure your mcast ip in sap and use multicast ping for testing