OK! I Give Up!
Sigh... I've tried to change the Java server to listen to port 22 directly. It works in the terminal in floor 4. But not in PC using the CSC lab network... T__T
I give it up. The admin is really... so trouble. Now I changed the ports to the default ones (i.e. 5800 and 5900 respectively). Both ports works in CSC. P.S. Port 22 is blocked inside CSC, but not terminals at floor 4.