SNEP (Simple NDEF Exchange Protocol)

What Is SNEP?

SNEP (Simple NDEF Exchange Protocol) is a lightweight application-layer protocol defined by the NFC Forum for exchanging NDEF messages between two active NFC devices in peer-to-peer mode. Built on top of LLCP (Logical Link Control Protocol), SNEP provides a simple request-response model for putting (sending) and getting (requesting) NDEF messages over an NFC peer-to-peer connection.

SNEP Architecture

SNEP operates at the top of the NFC peer-to-peer protocol stack:

SNEP uses LLCP's connection-oriented transport service (service access point 4) to ensure reliable, ordered delivery of NDEF messages. The connection-oriented mode provides acknowledgment and retransmission, guaranteeing that the complete NDEF message is received without corruption.

Protocol Operations

SNEP defines two primary operations:

PUT request. The client sends an NDEF message to the server. The server acknowledges receipt with a success or failure response. This is the operation used by Android Beam to push content from one phone to another.

GET request. The client requests an NDEF message from the server, optionally specifying an acceptable record type. The server responds with the requested NDEF message or an error if no matching content is available.

Message Format

A SNEP message consists of a compact header followed by the payload:

The maximum NDEF message size that SNEP can transmit depends on the negotiated LLCP MIU (Maximum Information Unit). With the default MIU of 128 bytes, large NDEF messages are fragmented across multiple LLCP information PDUs. SNEP handles this fragmentation transparently.

Response Codes

SNEP uses a simple set of response codes:

SNEP and Android Beam

The most widely known implementation of SNEP was Android Beam, introduced in Android 4.0 (2011). When two Android phones with NFC were tapped together, SNEP exchanged NDEF messages containing the current activity's content. For large transfers, Android Beam used SNEP only for the initial handshake, then handed off to Bluetooth or Wi-Fi Direct.

Although Android Beam was deprecated in Android 10 (2019), SNEP remains a required component of the NFC Forum Certification program. Devices must demonstrate correct SNEP client and server behavior as part of the certification test suite.

SNEP vs Direct NDEF Access

For tag-based NFC interactions (reader/writer mode), SNEP is not used. The reader accesses the tag's NDEF data directly through the tag's command set (READ, WRITE). SNEP is exclusively a peer-to-peer protocol for device-to-device NDEF exchange. Understanding this distinction is important when designing NFC systems: tag interactions use NDEF over the tag protocol, while device-to-device interactions use NDEF over SNEP over LLCP.