Dear Drees Far,

Yes. You have to make them listen on different ports

like this

server on 7.0

python openerp-server --addons-path ../7.0/openerp/addons --xmlrpc-port=7777

server on 8.0

python openerp-server --addons-path ../8.0/openerp/addons/ --xmlrpc-port=8888

or

for more information refer this link 

http://www.serpentcs.com/serpentcs-how-to-run-2-or-more-openerp-servers-on-same-machine

https://answers.launchpad.net/openobject-server/+question/189697

May be helpfull

Regards,

Ankit H Gandhi.