rollback doubt and connection to remoteDB

hi, some days ago I have a problem I want to solve.

The situation is the following:

I have a connection to a remote DB (with it's different from mine, of
course).
The querys I do are between sql-transactions

1 - Whate happens If during executing a query my pc loose the network
connection? what happens with the rollback?

Due to this time my pc that begun the query doesn't have the possibility to
invoke the rollback to the remote DB and cannot "clean" that DB

2 - Does exists any mechanism to do on the remote DB, or even a timeout that
if that timeout elapsed without any query from my pc, invoke any trigger o
event to "clean" the remote DB?

Thanks for your answers and if my question isn't clear, let me know

P.S: the postgres version I use is 8.2.3