Curiosity question here:
Are you behind some sort of firewall that would be
blocking the traffic based on port/protocol combos
or limitations? That's the first thing that springs
to mind when you mention the fact that it will work
on one but not the other. I haven't read the module
or the function so I don't know if a specific port is
used as a default or if you have the option of defining
one, but that might be a place to start looking for a
culprit.

-brick.