Gmod RCON not working

Hi

I am running a dedicated gmod sever (local machine) and I'm trying to add myself to fadmin. When I put the command in this is the reply to the console:

Socket connection failed <WSAEDDRNOTAVAIL>
Unable to connect to remote sever <0.0.0.0:0>

The command I am putting in is:

rcon add_user XXXXXXX

(X stands for username)


Please help

Thanks

Tom