The Short Message Peer to Peer (SMPP) protocol is an open industry standard messaging protocol designed to simplify integration of data applications with wireless mobile networks such as GSM, TDMA, CDMA and PDC. The protocol is widely deployed in the mobile telecommunications industry. The SMPP protocol specification is freely available from the Documents section of this site. With SMPP you can as an application developer send data to mobile devices or to the other applications over SMSC (Short Messasge Service Centre).
The protocol is based on pairs of request/response PDUs (protocol data units, or packets) exchanged over OSI layer 4 (TCP/IP session or X.25 SVC3) connections. PDUs are binary encoded for efficiency.
The most commonly used versions of SMPP are v3.3, the most widely supported standard, and v3.4, which adds transceiver support (single connections that can send and receive messages). Data exchange may be synchronous, where each peer must wait for a response for each PDU being sent, and asynchronous, where receiving and transmitting go in independent threads with the use of buffers and timers. The latest version of SMPP is v5.0.