Become root on the client side, and run the following command:
showmount -e serverHostName
You should get a response with something like this:
Export list for IPofServer:
where /mnt/nfs is the directory you are exporting from the nfs server, and
192.168.1.0/255.255.255.0 is the network (or machine) you are exporting it to.
I hope this helps.