Looking for sms modem over a network using IP address

Hello all,
I am looking for hardware that will allow me to send and receive sms but it will have to be connected to via its own IP address instead of a com port as the latter means our software cannot connect to it without moving the modem itself. Could anyone shed any light on the situation such as:
#alternatives
#What to look for
#where to buy

any help would be much appreciated