Android - What is a Data SMS?

Data SMS messages are sent through the data network, over your 2G / 3G data connection, just like all other data such as internet traffic. Normally SMS messages have their own method of transport, the details of which you can check out on Wikipedia.

A perfect example for data SMS use is when your recipient must pay to receive your text message even though you may have unlimited texting. By using a data SMS service, all extra charges are avoided and the amount of data used by SMS messages is insignificant compared to even lite web page viewing.

I think Data SMS messages are sent not only through the data network (over your 2G / 3G data connection), but also through GSM as Text SMS. The PDU of a text message has a User Data Headers (UDH) that defines a specific port on a handset. Refer to this link: http://developers.esendex.com/Concepts-and-Patterns/Sending-SMS-to-a-Specific-Port