A hitch warning is the server's way of saying "I had to think about something really hard and it caused some lag for the players". In other words, your cpu was getting maxed out. This normally happens during startup and map changes. If it happens in the middle of a round, your server is overtaxed.
If nobody is joining your server, all you are going to see is the heartbeats being sent. You can always check the server by typing "status" into the console.
"Do you expect me to talk?"
"No, Mr. Bond, I expect you to DIE."