Obs: Before any flaming user start saying "do your job/work/exercises instead of playing ", the computers isn't located at classroom, and I am "off-duty" when accessing".
All right, I am in a ubuntu 12.10 (I understand that makes things harder, but all the other computers use Ubuntu, so to decrease chances of detection, I put ubuntu too, but more updated, since the school's one is 11.04) accessing from my own hard drive (a pen drive with huge capacity), so root access and administration to edit files and connections aren't a problem. The connection here obviously have proxy blocks, firewalls and that kind of stuff to games, social networks, etc.
Changing the proxy and later using a VPS connection from SecurityKISS (OpenVPS) solved any kind of trouble while using the browser. Minecraft is updated (1.4.2) and running smoothly but I am only able to play in single player mode, since in multiplayer all servers appear with the error " Can't reach server " , which I am sure is the block's action.
Any suggestions or help appreciated.
See ya