Erlang ping on the internet

[mike h]

Hi,

I'd like to setup two erlang nodes and send messages to them over the internet. I'm having a few problems...
The network/hardware is:
I have a local PC, behind a firewall, connected to the internet.
I have a  remote system, behind a firewall,  hosted on the internet and I can ssh into it.
What I want to do is send messages between two erlang nodes, one on each system.

My local pc has a /hosts file like this.
w.x.y.z      mypc.home.net     mypc

My remote has a hosts file like this
a.b.c.d     ahost.mysite.co.uk

what is the erl incantation needed to start an erlang node on each system such that each can 
ping the other using net_adm:ping(...)? (I've tried various combinatiions of -name, -sname but failed).
And, of course, which ports do I need to open on the firewalls?

Going a little farther what other ports (if any) should I open to send messages between processes running on the local and remote nodes?

Thanks

Mike