To use the KDE talk daemon, update /etc/inetd.conf :

For example, on a linux system, if kde is in /opt/kde, set it to :
talk    dgram   udp     wait    root    /usr/sbin/tcpd  /opt/kde/bin/kotalkd
ntalk   dgram   udp     wait    root    /usr/sbin/tcpd  /opt/kde/bin/ktalkd