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Hack 63. Create an Internet Phone

Talk to the world and save money while doing
so.

As the number of broadband installs increases and the connections get
faster and faster, the potential to use quality audio and video
applications over the Internet has become more feasible. These kinds
of heavy-bandwidth applications are no longer the domain of just
large corporations with money to spend on expensive Internet access;
cable modems and DSL lines bring the technology to the home.

This hack explores how to use two applications to make phone calls to
others over the Internet. Although using these applications is fairly
straightforward, the configuration of firewalls and security can be a
barrier to getting started. In addition to exploring Internet-based
calls, I also discuss what options are available to call regular
phones from the Internet. A number of services offer PC-to-phone and
vice-versa services, and the cost compared to regular phones is often
minimal.

8.10.1. GnomeMeeting

GnomeMeeting is a fully open source
audio and video conferencing tool. This hack focuses on audio; [Hack #64] focuses on the use of
GnomeMeeting as a video conferencing tool.

When you use GnomeMeeting, a gatekeeper manages your connection. This
central server provides a directory of connected clients and their
call status. The gatekeeper offers a telephone directory-type service
for users, complete with a user profile. This hack
doesn't cover how to set up a gatekeeper, but
information on this is available at http://opengatekeeper.sourceforge.net.

Using GnomeMeeting is fairly simple if you have a working sound
cardjust connect to the default gatekeeper and go. Using
GnomeMeeting gets more complex when you roll a firewall into the mix.
GnomeMeeting requires a number of ports to be open on the firewall
for the software to work. Opening these ports can be a concern for
those who feel uncomfortable about providing additional access past
the firewall. Unfortunately, to use GnomeMeeting, you must ensure
these ports are forwarded to the machine running GnomeMeeting (or are
opened entirely if more than one machine will run GnomeMeeting), or
it won't work. One slight consolation is that you
can change some of the ports for different numbers by adjusting some
settings in GConf (the GNOME Configuration
program that comes with most GNOME installs). The ports to be
forwarded are as follows:

TCP port 1720

You can change this port if you modify the
/apps/gnomemeeting/ports/listen_port key in
GConf.

TCP port range 30000-30010

If you and the remote connection are using H.245 Tunneling, you
don't need to forward this range of ports. Microsoft
Netmeeting does not support H.245 Tunneling, so you do need to allow
and forward this range of ports if you need to connect to Netmeeting
clients. You can adjust this range of ports if you modify the
/apps/gnomemeeting/ports/tcp_port_range key in
GConf.

UDP port range 5000-5007

This mandatory range of ports is used for audio and video
transmission and reception.

UDP port range 5010-5013

These ports are used when registering to a gatekeeper. You
don't need to allow and forward these ports if you
don't plan on using a gatekeeper. You can change
this range of ports if you modify the
/apps/gnomemeeting/ports/udp_port_range key using
GConf.

Once you have set up your firewall to forward these ports [Hack #81], you must also ensure that
these ports are available to the outside world. Smoothwall includes
an External Services Access screen where you can configure this. If
you're accessing the Internet from a LAN, you should
turn on "Enable IP translation" in
the H.323 Advanced section of the GnomeMeeting preferences so that
GnomeMeeting can apply some processing to work over Network Address
Translation (NAT) routers. Previous versions of GnomeMeeting (0.94
and before) required that a special library called
RSIP (http://openresources.info.ucl.ac.be/rsip/) be
installed to achieve the same feature.

With the network settings complete, you can plug in your microphone.
Make sure the mic volume is turned up; many people forget to do this.
If you are using an ALSA-based setup, you can adjust the volume by
using alsamixer or the volume controls on your
desktop. With all of this complete, GnomeMeeting is ready to make
calls.

8.10.2. Skype

The new kid on the block in
the Voice over IP world is Skype (http://www.skype.com). This multiplatform
Internet phone uses proprietary peer-to-peer technology to provide an
efficient way of connecting to another client. If you
don't have a problem with the proprietary nature of
Skype, it is a highly recommended tool. The sound quality and
performance are simply incredible. One particularly interesting
feature about Skype is that it requires no port-forwarding or
adjustments to your firewall. This feature can be a saving grace for
those who have battled to get GnomeMeeting working and have found the
hill too steep to climb. Skype, by comparison, is a breeze to set up.

8.10.3. Calling Regular Phones

Both GnomeMeeting and Skype support PC-to-phone calls, but each has
a different method of dealing with these types of calls. In Skype,
you simply need to register a SkypeOut account, and then buy credits
that allow you to call regular phones. No additional software or
hardware is required.

If you want to call phones with GnomeMeeting, the process is more
complicated. First, you need to purchase some Quicknet hardware at
http://www.linuxjack.com. Due to
the patented nature of the G.723.1 audio codec that is required to
make phone calls, the codec cannot be included in the GnomeMeeting
code. But if you buy the Quicknet hardware, the codec is included in
the hardware itself, along with features, such as a speaker phone,
hardware support, and other niceties. Once you have installed the
hardware and it is working, you need to install the latest version of
the Open H323 driver from http://www.openh323.org. It is required to
make PC-to-phone calls. To actually make calls with GnomeMeeting you
need to register a MicroTelco account on http://www.linuxjack.com. This gives you a
login and PIN number that you can enter into the GnomeMeeting
settings. Finally, plug your normal phone device (analog phone,
cordless phone, etc.) into the Quicknet hardware, and dial the phone
as normal.