VPN + DNS-Enabler + Wide Area Bonjour = no success

Question

Hi,
what I am trying to do is broadcast the bonjour services of my home network such as file sharing, iTunes home-sharing and the like through my VPN connection. Since I am not too savvy with networking related topics I bought "DNS Enabler Snow" since it advertises to provide wide area bonjour with a minimum of setup hassle.
Now I am only getting so far that I can see my machine at home through VPN under "Network" in OS X. But I cannot connect. It always says "Connection Failed". Neither can I see my home iTunes library.
In the "Domains" section of DNS Enabler I entered:
Domain Name: <my DynDNS Domain>
Primary DNS Server: <my DynDNS Domain>
Host Name: <my DynDNS Domain>
IP address: <the local IP address of the machine running DNS Enabler>
In the bonjour section of DNS Enabler I entered:
Service Type: afpovertcp.tcp
Service Name: File Sharing
Host: <my DynDNS Domain>
Port: 584
TXT: path=/
Can anyone hint me at what might be wrong with this configuration?
Thank you!
Florian

Answer 1

I think the problem with the current setup is the use of the DynDNS hostname for the AFP service's hostname. When you're connected via the VPN you are effectively on the same network and so connection's attempted to the external-IP recorded by the DynDNS hostname will fail as it's not possible to loop back (for want of a better description) through the router. If you add a new A-record to the zone that points to the machines internal IP address and then change the service to point to the new record it should work via the VPN.
iTunes sharing won't work via this method as iTunes will only register and browse for services in the ".local" domain. The ".local" domain (a top-level domain like ".com") is only available via multicast-DNS. Multicast traffic as a general rule is not carried over a VPN (or the internet for that matter) as due to it's broadcast nature it can quickly clog up and cripple a network.
Hamachi unlike most VPN solutions presents itself as a virtual network interface that can carry multicast traffic which is why iTunes sharing works over a Hamachi connection. A cursory Google search tells me that multicast traffic can be carried over a OpenVPN connection with some additional configuration - your mileage might vary though.
Wide-Area Bonjour works by adding an additional domain to the system that software can then use for registering and browsing services. Unlike regular Bonjour, Wide-Area Bonjour works over the internet as it's based on traditional unicast DNS with a few extensions for updating records in realtime and NAT-PMP or uPNP (one or the other is in pretty much every router) for automatically setting up port-forwarding. If NAT-PMP or uPNP is not available, services can still be browsed but can not be registered (only services that can accessed via the internet are advertised); it's for this reason that Wide-Area Bonjour won't work properly in concert with a VPN. Whilst most OS X software is written to just register and browse in whatever domains are available there are some like iTunes that only register in the ".local" domain.
You can find out more detailed information about these topics at http://multicastdns.org/ and http://dns-sd.org/. I'm happy to answer any further questions you might have either here or via email. If my Wide-Area Bonjour service sounds like a good fit for you, please drop me a note and I'll let you know when I open-up the service to new users again (slated for mid-March).