Lifesteal is a private server, the IP address is not public. However, they have made a public Lifesteal server.
And if you get lucky, you may even encounter an actual lifestealer!
The Official Lifesteal Public Server is lifesteal.net!
If you want to play on the Lifesteal public server, it's always open.
Pro tip: Please don't trust random players if they want you to join their team when your new, they will SO take your heart!
For more info on it, go to the LSN Wiki as it has far more information on Lifesteal Net than you can find here.