Re: UDP Broadcast

[Doug Rogers <doug.rogers@...>]

Clark Snowdall wrote:
> require 'socket'
> host = "localhost"
> port = 47808
> udp, err = socket.udp()
> if not udp then print(err) os.exit() end
> udp:setoption('broadcast', true)
> err = udp:setsockname(host, port)
> if err == nil then print(err) os.exit() end

This might need to be changed to do what you want. Make sure you're not
getting a 'nil' printed on the screen - in which case the packet is
never being sent.

For a more reliable method of catching socket call errors, use assert():

  assert(udp:setoption('broadcast', true))
  assert(udp:setsockname(host, port))
  -- Do the same for the rest.

See http://www.lua.org/manual/5.1/manual.html#5.1 for the behavior of
assert(); the return values from the socket calls are designed to
interact with it for short scripts like this.

Also, for me udp:setpeername() fails under Linux when I use 'localhost'
in setsockname(). I have to set the host variable to be the local IP
address on the Ethernet interface (to which I want to send). I'm not
sure why this is so - perhaps use INADDR_ANY rather than 'localhost'?

If these are not your problems, then I'm at a loss. I was able to
capture the subnet broadcast packet using Wireshark; it's Ethernet
address was broadcast. I set the filter to 'udp port 47808' and made the
mods mentioned above.

Doug


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