Port blocking

[Mark Carter]

Supposing I decide to write a server-side application using something 
like corba or pyro.

What's the chance that in big corporations, the client's ports (in both 
  senses of the word: fee-paying, and application) will be blocked, 
thereby immediately scuppering whatever I have written? Has this problem 
ever arisen for anyone?

Also, is there a good tool for writing database UIs?