We have a web-based software which needs to communicate with EMV (http://en.wikipedia.org/wiki/EMV) device. We use Mozilla Firefox as our platform. Windows is the most important but the addon should, if possible, work also in Mac. EMV-device has a software which listens to TCP socket and sends the data to EMV device. So our program need to communicate with that software, so we need addon or plugin to handle the communication between our webpage and the TCP socket server in local machine. EMV-devices software uses XML to get commands and to send responses. Other versions of EMV-devices use either RS-232 or file based solutions (write a text file to specific directory). We are also interested in these solutions once the socket one is ready. Keywords: Software, Javascript, Mac, Architecture, OS, Window, Desktop