IP Multicast Channel
Syntax
dp_connect ipm -group ipAddr
-myport myPort -ttl numHops
Comments
IPM is the multicast version of UDP. It allows any
number of machines to join a group and if a message is sent to
the group address, all the machines will hear it.
- ipAddr is the IP address of the group.
This must be an multicast address in the range of
224.0.0.0 to 239.255.255.255.
- myPort is the local port and is optional.
- numHops is the Time To Live value. The
multicast packets will only cross numHops-1
routers after which they are discarded by the
router. To keep all multicast data on the local
subnet, use a ttl value of 1. Proper netiquette
maintains that this number be as low as possible.
It is optional and defaults to 1.
One can add and drop IPM group memberships using the
fconfigure -group command. See below for examples and please note
the use of the plus and minus symbol to signify add or drop. An
IPM channel can be a member of any number of multicast groups
(although it is usually limited by the OS to 20) so it is not
necessary to drop a group in order to add a new one.
Examples
- dp_connect ipm -group 224.76.0.119
- dp_connect ipm -group 225.23.120.87 -ttl 3
- dp_connect ipm -group 238.1.1.1 -port 1905 -ttl 255
- fconfigure $ipmChan -group +226.54.3.2
- fconfigure $ipmChan -group -232.56.198.6