How to easily determine, which outbound ports aren't blocked by firewall
This website comes in handy for that:
http://portquiz.net:1234/
This example tests whether you are able to visit outbound port 1234. You simply change the port number to whatever you like. Also, the site gives some examples that could be used in a command line script:
$ wget -qO- portquiz.net:1234
Port 1234 test successful!
Your IP: 198.252.206.16