What SMS app. is used in asterisk for softphones in LAN?

Hi all,

I read on net that asterisk uses SMS() application defined in app_sms.so to send/receive SMS from fixed line phones.

But, i want to send/receive SMS between instant messaging enabled softphones via asterisk. As softphones are connected via asterisk.

So, please guide me which application asterisk uses for above specified purpose.
Please help,
I need it.
Waiting for response.

Thanking you.