The aim of this report is to deal with the main important topics of the communication system of a prototype developed in order to detect when commercials on television finishes, and warn users interested in this kind of events. This project has been totally assembled de novo by developers, and for this reason the first sections of this report are about analysis, requirements and design of the system. In order to develop the communication part filling all the requirements, which are going to be explained, an extension of XMPP (Extensible Messaging and Presence Protocol) protocol was chosen and adapted. It would provide us push-type connections between client and server side. With the aim of testing the proper functioning of the system, and ensure the first pleasant interface to users, a visual client application in Java has been also developed. Finally, there is a description of the tuning process of the prototype: configurations of different machines that have been set up, mainly OpenFire (XMPP server) and Apache Tomcat (used to create plugings and connectors). Note that all software components used are Open Source type. Inside this report you will not find any reference to topics related to image treatment or processing, neither DVB-T concepts. They can be found in a report with the same name, written by Jordi Coscolla Álvarez, at FIB (Facultat Informàtica Barcelona).