1Test IPv4 multicast packets. 2 3Use two programs to send and receive multicast packets. After 4setting up the socket, the receiver forks and execs the sender to 5avoid races. If the test fails, the receiver runs into a timeout. 6 7The test programs are: 8mcsend - send one multicat UDP packet 9mcrecv - receive one multicast UDP packet 10mcroute - route one multicast UDP packet 11 12The options for mcsend and mcrecv and mcroute are: 13-b fork to background after setup 14-f file print message to log file, default stdout 15-g group multicast group, default 224.0.0.123 16-i ifaddr multicast interface address 17-l loop disable or enable loopback, 0 or 1 18-m message message in payload, maximum 255 characters, default foo 19-n timeout expect not to receive any message until timeout 20-p port destination port number, default 12345 21-o outaddr outgoing interface address 22-r timeout receive timeout in seconds 23-t ttl set multicast ttl 24mcsend ... after setting up receive, fork and exec send command 25 26With mcroute packets are sent over a multicast router. The kernel 27route is installed statically. The machines sender, router, receiver 28are involved. Receiver is on the local machine, route is on remote 29machine. The sender can share the local machine or be started on 30a target machine, depending on the setup. This is controlled via 31environment. 32