Building a Call Center with LTSP and Soft Phones

CFLAGS=-I/usr/X11R6/include -I/usr/qt/3/include \
  -Wall -O3 -I. -I../gsm -I../ilbc -I../dissipate2 \
  -D_REENTRANT=1 -DQT_THREAD_SUPPORT=1 \
  -DHAVE_LIBX11=1 -DHAVE_LIBXEXT=1 -DHAVE_LIBXT=1 \
  -DHAVE_LIBICE=1 -DHAVE_LIBSM=1 -DHAVE_LIBPNG=1 \
  -DSTDC_HEADERS=1 -DHAVE_FCNTL_H=1 \
  -DHAVE_SYS_IOCTL_H=1 -DHAVE_UNISTD_H=1 \
  -DHAVE_SELECT=1 -DINCLUDE_STDLIB_H=1 $(MOREDEFS)

To run KPhone, we put a script in /usr/bin on the terminal server called kphone (Listing 5). This script simply opens access to the xserver, determines the terminal at which the user is sitting and starts the KPhone process on that terminal.

#!/bin/bash
xhost + > /dev/null
HOST=`echo $DISPLAY | awk -F: '{ print $1 }'`
export HOST
ssh ${HOST} env DISPLAY=:0.0 /bin/kphone

To make things easier for the users, we created an entry in the KMenu for KPhone that they can select or move onto their docks if they wish. This entry is created by adding the file kphone.desktop (Listing 6) to /usr/kde/3.3/share/applications/kde on the terminal server.

[Desktop Entry]
Comment=
Exec=kphone
GenericName=Office Telephone
Icon=/usr/kde/3.3/share/icons/Locolor/32x32/apps/kab.png
Name=kphone
Path=
StartupNotify=true
Terminal=0
TerminalOptions=
Type=Application
Categories=Qt;KDE;Office
X-KDE-SubstituteUID=false
X-KDE-Username=

The user then can select the KPhone menu item and launch KPhone (Figure 1). The first time the application is run, the user has to select File→Identity to open the Identity dialog (Figure 2) and enter the connection information. The data to enter here must match that information for the SIP accounts on the VoIP server (Asterisk in our case). Because KPhone stores its configuration in the user's home directory, it need be configured only the first time the user starts KPhone. Because /home is NFS-mounted from the server, the station where users log in is their phone, so the phone effectively follows them if they should change workstations. Once users have registered with the server, they can make calls from the call dialog and DTMF panel (Figure 3).

Figure 1. The user's desktop environment runs on the LTSP server, but KPhone runs locally.

Figure 2. When first running KPhone for a new user, enter the information for the Asterisk server.

Figure 3. The KPhone call dialog works like a hardware phone.

Initially we had KPhone running, but the response time for any action was horrible. Any time the user would perform an action that caused an SIP message to be sent—dial a number, press a phone button on an active call, answer or hang up the phone—it would take nearly a minute for the action to occur.

We determined that this problem was occurring because of a DNS name resolution issue that was waiting to timeout. The solution was to put entries into /etc/hosts for each of the stations that would be running KPhone, install dnsmasq on the terminal server and have the terminals reference the terminal server as their DNS server, configured in dhcp.conf. There are other, perhaps better, ways to solve this issue, but this solution took minimal time to configure and run, and it worked. Finding the source of the problem was the hard part.

There have been a couple drawbacks to this system. Occasionally KPhone closes for no given reason, which can be quite annoying. We have not yet determined the cause of this problem, and we hoped that upgrading KPhone to 4.1 might help.

The KPhone package.def file contains the necessary lines for building KPhone 4.1.1. The change to the Makefile mentioned above for 4.0.5 still applies as of 4.1.1. Our preliminary tests indicate, however, that 4.1.1 has the same problem of closing suddenly for an unknown reason. We have inquired with the maintainers of KPhone to see if they can help, but so far we do not know the cause of the problem.

Another drawback is that when the phone rings, it rings through the headset and gives a visual alert on the screen. If users are not in front of their terminals with their headsets on, they will not know that their phones are ringing. Once the call center is in full operation, operators probably will spend most of their time at the terminals, so this may not be a problem.