Short phone calls "on the cheap"

Some of you may have already installed your own small PBX using Asterisk, maybe by your own, maybe as part of any of the growing popular wireless communities.
With a little configuration we'll take the capability of make short calls (at least 60 seconds) for free to some countries.

Days later I was told by an academic friend about VoIPBuster. These people sell you prepaid VoIP calls from your Windows based computer, using a softphone freely downloadable from their web page.
The interesting part in this, is that once you have registered to use their softphone, you can call to landlines (sorry people, no cellullar by now) for free in most of the countries they have service available. Even more interesting it's the fact that in case you don't buy credit from them, you're still available to make these calls for free, but with a time limit of 60 seconds.

Up to here I find it quite interesting, but having to dial with a Windows softphone it's a nono for me... and considering I already have one of those asterisk installations I already mentioned.

After making some search, it seems that they are known under other commercial names with different domains, like VoIPstunt. There seems to be more names, but it's not interesting to post them all here. However, every bussiness name has its own dialer, and your login doesn't work between them. You have to register new accounts under every domain.
You may notice that every domain has a different list of countries where you can call for free, so it's a good advice to register and setup an account in more than one of their domains.
So, once I've downloaded the VoIPbuster softphone, we proceed to install it on a Windows system, I registered for a new account (by the moment I buyed no credit, though if you keep using this service it's recommended to buy some, it's quite obvious if you'd like for this service to keep). The installation is quite simple, the traditional click and follow installer, followed by the registration process. After that I tried to make that free call with the softphone and it worked successfully.
Helped with the beloved 'tcpdump' I noticed that the ports used by the softphone are standard SIP ports (if you kept reading up here, you probably are aware of what SIP is), and the IP address where it's sending data. So, with that precious information, I proceeded to try some configurations on my asterisk box:

First I added the following to my sip.conf:


and then in extensions.conf this snippet:

exten => _9XXXXXXXX,1,Dial,SIP/0034${EXTEN}@voipstunt
exten => _8XXXXXXXX,1,Dial,SIP/0034${EXTEN}@voipstunt
exten => _00.,1,Dial,SIP/${EXTEN}@voipstunt

in the same file, under the appropiate context (for example local-access if it's okay with you):

include => voipstunt

And guess what... We're now able to dial spanish landlines (usually beginning with 9 or 8) or international calls (dialing 00 before your called party). By now the calls are limited to 60 seconds, but I recommend you to buy some credit to keep this service available, and after that these calls drop the time restriction. Keep in mind that the amount of prepaid calls you buy is not used with these landline calls, but you have to spend it somehow because it expires after some months (this is explained accurately in any page of those VoIP service providers).

That's it, now you can wish merry Christmas to those Japanese pals... ;-)