Which port to use for my registration app?

I have written a small product registration app.

What happens is the user enters their details, and all their info is sent to our database server. The db server is running MySQL and is running on port 77330.

Now what happens if somebody installs my software, but their organisation has port 77330 closed on the firewall? I assume my registration app won't work?

Then what port does apps like Norton Liveupdate and other software registration apps use?

I am connecting directly to my database server and running an insert query directly from the app, is this the correct way to do it? Or is there a better way?

Thanks