SMPP

Short Message Peer-to-Peer Protocol (SMPP) is an open, industry-standard protocol for exchanging SMS messages between external short messaging entities (ESMEs) and short message service centers (SMSC), typically over TCP/IP. It was developed in the 1990s by Aldiscon and has since become the de facto protocol for high-throughput SMS interworking. The SMPP Forum maintains the official specifications.

SMPP operates as a binary, session-based protocol using a request–response model. Messages are sent as protocol data units (PDUs) with a fixed header and a variable-length body. Clients bind to an SMSC using BindTransmitter, BindReceiver, or BindTransceiver, after which they submit messages with SubmitSm and receive DeliverSm for inbound messages or delivery receipts. Other PDUs include QuerySm, CancelSm, and ReplaceSm, while EnquireLink checks the connection.

SMPP supports two-way messaging, concatenated messages via user data headers, and multiple data codings including 7-bit, 8-bit, and UCS-2 (Unicode). It is designed for high throughput, allows multiple parallel connections, and is widely used by mobile operators, SMS gateways, and enterprise messaging platforms. Security is not built into the protocol; encryption and integrity are typically provided by the underlying transport such as TLS or VPN.

Common versions include SMPP 3.3, SMPP 3.4, and SMPP 5.0, with 5.0 introducing optional parameters and more flexible addressing and error reporting. The protocol remains in widespread use due to its performance, simplicity, and extensive ecosystem of gateways and aggregators.