protocol-sp

Pure Ruby codec and connection for the Scalability Protocols (SP) wire format used by nanomsg and nng. Zero runtime dependencies. Sister gem to protocol-zmtp.

• Protocol::SP::Codec::Frame — length-prefixed framing. SP/TCP uses an 8-byte big-endian length; SP/IPC prepends a 1-byte message type (0x00 control, 0x01 user) to match nng's wire format.
• Protocol::SP::Codec::Greeting — 8-byte handshake: 00 'S' 'P' 00 <peer-proto:u16-BE> 00 00.
• Protocol::SP::Protocols — protocol identifier constants (PUSH=0x50, PULL=0x51, PUB=0x20, SUB=0x21, REQ=0x30, REP=0x31, PAIR_V0=0x10, PAIR_V1=0x11, BUS=0x70, SURVEYOR=0x62, RESPONDENT=0x63).
• Protocol::SP::Connection — mutex-protected #handshake!, #send_message, #write_message (no flush), #write_messages (batched under a single mutex acquisition), #receive_message over any IO-like object. framing: selects :tcp or :ipc.

• SP messages are single-frame (no multipart, unlike ZMTP).
• No security mechanisms in the SP wire protocol — encryption is layered via TLS/WebSocket transports, not the SP framing.
• No commands at the wire level — protocol-specific control bytes (e.g. REQ request IDs, SUB topics) live inside the message body.
• Zero-alloc frame headers on the unencrypted hot send path via Array#pack(buffer:).

protocol-sp is a low-level codec. For a full socket API (PUSH/PULL, REQ/REP, PAIR, transports, reconnect), see nnq.