SMPP
Short Message Peer to Peer (SMPP) is an open, industry-standard protocol for sending text message (SMS) data over the Internet.
It is used primarily for connecting third-party services with SMS centers, enabling various types of automated SMS services. It is also used to link SMS center gateways, enabling inter-carrier messaging.
A newer, XML-based standard with similar functionality exists called MMAP, which may replace SMPP.