Introduce new signature for both `dgram.createSocket` method and
`dgram.Socket` constructor:
dgram.createSocket(options, [listener])
Options should contain `type` property and may contain `reuseAddr`
property. When `reuseAddr` is `true` - SO_REUSEADDR will be issued on
socket on bind.
fix#7415
Signed-off-by: Fedor Indutny <fedor@indutny.com>
Passing the number of sent bytes to the callback is superfluous;
datagram sockets operate in atomic mode: either the sendmsg() system
call succeeds or it fails but it never does partial writes.
Instead, report send errors to the callback. UDP error reporting is
fairly haphazard on most platforms. You should not expect reliable
delivery of anything besides EMSGSIZE and (possibly) ENETDOWN and
ENETUNREACH.
Fixes#2608.
These are options needed for real-world multicasting.
Implementation notes:
- POSIX only.
- IPv4 only (IPv6 multicast is a tricky beast).
- Didn't update tests, because it can't effectively be demonstrated on
localhost only.