What is the correct way to initialize a UDPSocket for only sending broadcast packets?
I wondered if this would work:
julia> usock=UDPSocket()
UDPSocket(init)
julia> send(usock, ip"255.255.255.255", 42000, "test")
ERROR: IOError: send: permission denied (EACCES)
Stacktrace:
[1] uv_error at .\libuv.jl:85 [inlined]
[2] send(::UDPSocket, ::IPv4, ::Int64, ::String) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Sockets\src\Sockets.jl:354
[3] top-level scope at none:0
And that error makes sense. On v1.0.1, I tried to use Sockets.setopt and that yields a different issue:
julia> usock=UDPSocket()
UDPSocket(init)
julia> Sockets.setopt(usock; enable_broadcast=true)
ERROR: IOError: enable_broadcast: bad file descriptor (EBADF)
Stacktrace:
[1] uv_error at .\libuv.jl:85 [inlined]
[2] #setopt#4 at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Sockets\src\Sockets.jl:266 [inlined]
[3] (::getfield(Sockets, Symbol("#kw##setopt")))(::NamedTuple{(:enable_broadcast,),Tuple{Bool}}, ::typeof(Sockets.setopt), ::UDPSocket) at .\none:0
[4] top-level scope at none:0
I can get around this by:
- Making a
UDPSocket - Sending a ‘throw-away’ packet to localhost
- Using
Sockets.setopt, setenable_broadcast = true - Finally send a packet on the broadcast address
I’ve confirmed this works (see below), but is this the preferred way to actually set up and use a UDPSocket for broadcast?
On the receive side:
julia> using Sockets
julia> usock=UDPSocket()
UDPSocket(init)
julia> bind(usock, ip"0.0.0.0", 42000)
true
julia> apkt = String(recv(usock))
"actual_payload"
julia>
On the send side:
julia> using Sockets
julia> usock=UDPSocket()
UDPSocket(init)
julia> send(usock, ip"127.0.0.1", 0, "test")
julia> Sockets.setopt(usock; enable_broadcast=true)
julia> send(usock, ip"255.255.255.255", 42000, "actual_payload")
julia>