One problem that always seems to plague the JJ2 community is that of the pinging server. It's very frustrating when you host your amazing new level, and no one is able to join and admire. I have had this problem myself, but stumbled on a brilliant, elegant solution:

Step 1: Mess with your router's settings and break the internet for your family.

Step 2: Keep playing with the router until it somehow starts working.

Step 3: Forget how you fixed it before the router automatically resets itself in a week or two, and be unable to replicate your first successes.

Step 4: Go to college for a year, and continue to have hosting problems.

Step 5: Give up on hosting.

Step 6: Stop playing Jazz for several months.

Step 7: Move into a new apartment.

Step 8: Dust off JCS and try to make a quick little level for a fun looking contest.

Step 9: Forget entirely how to do stuff like make jailbreak levels.

Step 10: Create a server called "Don't Join" late at night, with an awful, malfunctioning skeleton of a level, assuming the pinging or the name will allow you to test stuff without people seeing how hard you fail at level making now.

This should guarantee that your server stops pinging and people join. 100% of people I know who followed these instructions could host afterwards. Also, to make sure you continue to be able to host, be sure to follow step 11: Post about your success, jinxing your success.