Protocol & Messages

aiosignalr.protocol

IHubProtocol

Interface implemented by JSONProtocol and MessagePackProtocol.

• name — "json" / "messagepack".
• version — protocol version (2).
• transfer_format — TransferFormat.TEXT / BINARY.
• write_message(message) -> bytes — serialize one message into a frame.
• feed(data) -> list[HubMessage | None] — parse complete frames from a byte stream.
• create_parser() -> IHubProtocol — fresh connection-bound instance.

JSONProtocol

Text protocol. Each message is one JSON object terminated by 0x1E.

MessagePackProtocol

Binary protocol. Each message is a MessagePack array prefixed by a VarInt length.

Handshake helpers

• encode_handshake_request(protocol, version) -> bytes
• encode_handshake_response(error=None) -> bytes
• HandshakeParser — incremental, record-separator-delimited parser.
• parse_handshake(frame) → HandshakeRequestMessage | HandshakeResponseMessage.

aiosignalr.messages

Immutable (frozen, slots) data classes for every hub message:

Class	message_type	Fields
InvocationMessage	INVOCATION	target, arguments, invocation_id, stream_ids, headers
StreamInvocationMessage	STREAM_INVOCATION	target, arguments, invocation_id, stream_ids, headers
StreamItemMessage	STREAM_ITEM	invocation_id, item
CompletionMessage	COMPLETION	invocation_id, error, result, has_result
CancelInvocationMessage	CANCEL_INVOCATION	invocation_id
PingMessage	PING	—
CloseMessage	CLOSE	error, allow_reconnect
AckMessage	ACK	sequence_id
SequenceMessage	SEQUENCE	sequence_id
HandshakeRequestMessage	—	protocol, version
HandshakeResponseMessage	—	error

aiosignalr.message_buffer.MessageBuffer

The shared stateful-reconnect buffer (see Stateful Reconnect). Used by both client and server.

MessageBuffer(
    protocol: IHubProtocol,
    write: Callable[[bytes], Awaitable[None]],
    *,
    buffer_size: int = 100_000,
    ack_interval: float = 1.0,
)

Method	Description
async send(message, data)	Buffer a trackable message and write it
async send_serialized(data)	Buffer a pre-encoded frame (broadcast fanout)
should_process(message) -> bool	Dedupe / gate inbound messages
ack(message)	Drop buffered messages ≤ ack sequence id
disconnected()	Enter reconnect state (ignore non-sequence messages)
async resend()	Send Sequence + replay the buffer
dispose()	Cancel the pending ack timer

aiosignalr.framing

• encode_text_message(data) -> bytes — append 0x1E.
• TextMessageParser(max_size) — incremental 0x1E-delimited parser.
• encode_binary_message(payload) -> bytes — VarInt length prefix.
• BinaryMessageParser(max_size) — incremental length-prefixed parser.