Protocol specifications

Contents

• Protocol specifications

  • Greetings

  • Outgoing frames

  • Pings (keep-alive frames)

  • Incoming frames

    • Acknowledgements

    • Messages

    • Topic publications

Greetings

server: EB 01 00

client: EB 01 00

server: 01 or 75 if not supported and closes

client: XX XX (len) ID (string-utf8-bytes)

server: 01 (OK) or XX (error code) and closes the connection

Outgoing frames

client: XX XX XX XX (OP-ID-CUSTOM) FLAGS XX XX XX XX (frame len) TARGET 00 PAYLOAD

FLAGS = u8, first 6 bits - op, last 2 bits = QoS (0 - no confirm, 1 - confirm processed)

Operations:

• 0 - NOP (ping)

• 1 - publish to topic, target = topic

• 2 - subscribe to topic(s), no target required

• 3 - unsubscribe from topic(s), no target required

• 0x12 - direct message

• 0x13 - broadcast message

Pings (keep-alive frames)

client: XX XX XX XX 00 XX XX XX XX

where XX - any bytes (so 0x00 * 9 is fine)

the client should ping the server to make sure the connection is alive. the server may ping the client, no reply is required.

Incoming frames

first 6 bytes:

• 0 - frame type

• 1-4 - frame len or op id

• 5 - reserved or ack result

Acknowledgements

The server sends acks for all operations with QoS > 0

server: FE XX XX XX XX (OP-ID-CUSTOM) 01 (OK) or error code

Messages

server: 0x12/0x13 XX XX XX XX 00 (frame len) SENDER 00 PAYLOAD

Topic publications

server: 01 XX XX XX XX 00 (frame len) SENDER 00 TOPIC 00 PAYLOAD