Sometimes workplaces setup draconian firewalls which block urls, and don't let you get out on ports other than 80 and 443. As a developer this is a bit restrictive...

I wanted to run a GUI application (AIX) on a local cygwin XServer (Windows) but always got a XWin: client # rejected from IP address error message appearing in the log file (%cygwin_root%\tmp\XWin.log). I looked over the FAQ and user guides on cygwin's site but to no avail. Even googling wasn't really much help. Thankfully I stumbled upon the answer in a tangential link of interest about CoLinux.