how to get a multicasting application to work
 

hey i wanted to do multicasting i.e. write multicasting application for educational purpose.i even tried to run few codes from different tutorial in c as well as java but thing didn't worked.then i discovered that there are different level of compliance of multicasting capability some say that linux is level 2 compliant and you need to execute some command of "route ***" which i don't understand but i guess has to do with making entries in routing table understand while others say that you will have to recompile your kernel and install mrouted which for me could be a great deal of work.so i just wanted to now what all is required for multicasing over lan and over internet

Nothing special required to do MULTICAST, note that mrouted is only used if you want that your linux box run as a MULTICAST router, nothing to deal with just sending and / or receiving MULTICAST datagrams.

Some tricks:
-you can add the multicast route into the kernel routing rules, but as far as i know it can be a problem only if you have more than interface, or if your default interface isn't configured. That said, you can add it with the following command as root:
, you can replace "eth0" with any other interface you want.

-You can overwrite the system routing rule in your program by specifying the IP address of the interface to use to "listen" to the MULTICAST group when you "setsockopt (IP_ADD_MEMBERSHIP)", and for the emitting interface with a "setsockopt (IP_MULTICAST_IF)". The emitting and receiving interface are totally independant.

-Your MULTICAST emitter doesn't need to make a "setsockopt (IP_ADD_MEMBERSHIP)".

-If the emitter and the receiver run on the same system, you need to loop the MULTICAST socket with a "setsockopt (IP_MULTICAST_LOOP)"

If these don't help, post your code I'll take look.