Monday, May 26, 2008
A Phone Call From Ralf
Today I recieved a phone call from Ralf, a friend of me and some of my other acquantances. The thing that was unusual about the call was that it was the first I have recieved using Voice Over Internet Protocol (VOIP) / Session Initiation Protocol (SIP). I've placed many outgoing calls in the past but never recieved any till today. The call was using the services and accounts of the Gizmo Project (http://www.gizmoproject.com) by both of us. One of the cool things I like about Gizmo's service is that if you are not logged in with it, and you recieve a call, they will email you a .wav file of any voice message a caller leaves for you, effectively turning your inbound email into an answering machine. I've played these wav files with mplayer while browsing my email's web interface with Lynx. I consider this an indication of keeping things interoperable by sticking with basic, universal protocols and formats. I'd just gotten outgoing calls using my Gizmo account to work yesterday with the Linphonec client, from the Debian Linux distribution package linphone-nox. This particular client is a text console application that simply presents you with a prompt to type in commands, and does offer a 'help' command to get a list and further details of possible commands as well as tab completion. In general the commands are fairly straight forward, but I do have a few complaints. It does not respond to 'exit', you must type in 'quit' to leave the program. There is no command to toggle muting on the microphone, so I have to put it in a wrapper alias to handle this with an 'amixer' command I figured out to work with my particular sound card. This probably varies from soundcard to soundcard. Also there is no direct command to dump the call log (the output of the 'call-log' command) into a file for saving. There may be a switch, '-l
' to handle
saving the logfile, but that will need to be folded into the wrapper
alias, so it has to be thought out a head of time.
One of the things that was notable about the call was
that it traversed three firewalls, two of them
performing NAT (Network Address Translation).
There had been some adjustments to these firewalls to handle
the outgoing calls, but apparently that was sufficient to
enable incoming calls. NAT is frequently considered the
bane of VOIP, but apparently, at least on a limited scale,
it can be dealt with.
Anyway, before the day ended I'd recieved
several other calls from Ralf and another friend
further confirming that the combination of software,
hardware and protocols provided functioning