InstaMsg allows persistent connections over TCP and Web Sockets using the MQTT protocols. It uses the following ports:
Port 1883 for TCP connections
Port 8883 for secure TCP connections
Port 80 for WebSockets
Port 443 for secure WebSockets
TCP/IP port 1883 and 8883 is reserved with IANA for use with MQTT.
For all other Client Libraries MQTT port 1883 and 8883 is used. You might have to open these ports for running these Clients behind firewalls. We are in process of building support for WebSockets on all Client libraries so that you can switch to WebSockets if you have issues opening these ports on your firewall.