Mcastsend / mcastrecv: Efficiently sends a file to multiple machines with multicast
The recieving ends connect back to the sending end to get the filename, checksum, and multicast address; this connection is also used afterwards to get any chunks that were missed in the multicast.
You can have the sending end wait for either a specific number of clients to connect, with -n, or wait a certain amount of time then transmit to the clients that have connected with -t. You must specify one of these options.
The recieving end just needs to know what to connect to; it gets the local filename from the sender.
The SHA1 hash of the file is sent with the filename; it's checked before the client reports OK to the sender and overwrites the old file.
Unless you've got a really fast network you'll also want to specify a rate, or lots of packets will get dropped. Do that with -r; you can specify it in gb, mb or kb per second.
The sending end needs the defaulte route for multicast traffic, like so: route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0. This should be done by default in modern distributions, but it's not.
- TODO
- Figure out why it sends slower than you tell it.
Maybe fix theoretical security problems (the receiver ought to at least check the source address on UDP packets).
Add an option to specify the multicast group.
Make it use a random high number port, instead of a fixed port?