Controlling a Battlefield 3 server is best suited to Procon. You can obtain the software from http://phogue.net.
After launching Procon, click "Create Connection" on the right of the program's start page.
You should complete the fields that now appear as follows:
Hostname/IP: IP of the game server without the port
Username: Leave this field blank
Password: The server's Rcon password
Then click "Connect".Tags: Battlefield