Connecting VB.net Applications to each other

I am building a VB.net application which is supposed to serve as a Mission Control Center for our virtual aviation community's Space Shuttle Program. In this direction, I will have 20 people using this "MCC" to follow the shuttle. Within the MCC, I must connect all of the 20 open programs to each other so that for example if one presses the "EMERGENCY" button, all of the others will be notified. Also, I need to add an Instant Messaging or Telephony (VoIP) to this application. Currently, the way I'm doing it is: If one presses "EMG", this executes a PHP file on my server and the PHP file produces a text file which is being downloaded every 1 minute by every user. The software then interprets the message as EMG, emergency, and flashes a red light. But for every user, this will have a maximum 1 minute delay... This is SO amateur and it sucks because you have a 1 minute delay in notifications... How can I do this more efficiently. Please consider the fact that other users won't be able to do advanced stuff like opening ports for P2P connections. Thanks!