Please add a function to join an UDP multicast group

[ufechner7]

Joining a UDP multicast group is not yet supported by Julia.
Probably it requires just one operation system specific function call to set the correct options.
We really need this!
Uwe

[Paul-at-home]

This worked for me.

Create the socket:
s = UDPSocket()

Bind:

bind(s, ip"multicast IP", port_no)

Join the multicast group:
ccall(:uv_udp_set_membership, Cint, (Ptr{Cvoid}, Ptr{UInt8}, Ptr{UInt8}, Cint), s.handle, "multicast IP", C_NULL, 1)

Get a message:
msg = recv(s)

Leave the multicast group:

ccall(:uv_udp_set_membership, Cint, (Ptr{Void}, Ptr{UInt8}, Ptr{UInt8}, Cint), s.handle, "multicast IP", C_NULL, 0)

[StefanKarpinski]

If someone wants to take these C calls and turn them into an API we'd be happy to have them.

[Paul-at-home]

Sorry - I don't feel qualified to put it into the API!

I would add that in this call:
ccall(:uv_udp_set_membership, Cint, (Ptr{Void}, Ptr{UInt8}, Ptr{UInt8}, Cint), s.handle, "multicast IP", C_NULL, 0)

C_NULL refers to the interface from ifconfig command line. C_NULL takes default.