UDP socket receive question

[Martin Pirker]

Hello...

Copying the minimalistic UDP receive example from the online Pickaxe I

require 'socket'
port = 12000
server = UDPSocket.open
server.bind(nil, port)
loop do
text,sender = server.recvfrom(1024)
puts text
end


localhost --> localhost UDP connections work fine


so I tried connecting 2 different boxes
check network connection by netcat:

sender: echo "whatever" |netcat -u 192.168.x.y 12000
receiver: netcat -u -l -p 12000
connection is ok

receiver netcat and sender Ruby script work ok, too


but, with receiver Ruby (like above) neither sender netcat nor Ruby
script are able to make a transfer -> Ruby receiver drops pakets?!?

lsof shows a "UDP localhost:12000" binding, so everything should be ok
on the receiving side


Question:
I simply want a Ruby script collecting all UDP pakets arriving at a
specific port, above script only works for me localhost-->localhost
why?


ruby 1.8.2 (2004-07-16) [i686-linux] (aka pre1)


thanks for any hint, I'm out of ideas
Martin

 

[Joel VanderWerf]

Hello...

Copying the minimalistic UDP receive example from the online Pickaxe I

require 'socket'
port = 12000
server = UDPSocket.open
server.bind(nil, port) ^^^

loop do
text,sender = server.recvfrom(1024)
puts text
end


localhost --> localhost UDP connections work fine


so I tried connecting 2 different boxes
check network connection by netcat:

sender: echo "whatever" |netcat -u 192.168.x.y 12000
receiver: netcat -u -l -p 12000
connection is ok

receiver netcat and sender Ruby script work ok, too


but, with receiver Ruby (like above) neither sender netcat nor Ruby
script are able to make a transfer -> Ruby receiver drops pakets?!?

lsof shows a "UDP localhost:12000" binding, so everything should be ok
on the receiving side


Question:
I simply want a Ruby script collecting all UDP pakets arriving at a
specific port, above script only works for me localhost-->localhost
why?


ruby 1.8.2 (2004-07-16) [i686-linux] (aka pre1)


thanks for any hint, I'm out of ideas
Martin

 

[Eric Hodel]

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^^^
Try a hostname here? You can use the string '<any>'. I guess that
means any interface.

No. nil means bind to all interfaces. See getaddrinfo(3).

--
Eric Hodel - (e-mail address removed) - http://segment7.net
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[Joel VanderWerf]

No. nil means bind to all interfaces. See getaddrinfo(3).

Ok, but UDPSocket#bind accepts '<any>' as well. It appears (from brief
groping in etx/socket/socket.c) that nil and '<any>' are synonyms. So
substituting one for the other will not make a difference in the problem
the OP was trying to fix.

 

[Martin Pirker]

Ok, but UDPSocket#bind accepts '<any>' as well. It appears (from brief
groping in etx/socket/socket.c) that nil and '<any>' are synonyms. So
substituting one for the other will not make a difference in the problem
the OP was trying to fix.

but it does fix it

nil gives a "UDP localhost:12000" binding according to lsof

"<any>" and "" gives a "UDP *:12000" binding and appears to work as
expected => accepts any packet arriving from any sender at this port


question is, why I didn't find this myself?

I assumed nothing set aka nil means "don't bind to anything, accept
everything", so I just copied from the example
reading the "socket-level access" paragraph at the beginning points
one to "" as INADDR_ANY, but nowhere a word of "<any>" or a definiton
of nil ?

thanks! always nice&helpful ppl here,
Martin