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Errors

All exceptions inherit from SignalRError (which itself inherits from Exception), so you can catch every library error with one base class.

Exception
└── SignalRError
    ├── ProtocolError
    ├── HubException
    ├── ConnectionClosed
    ├── ServerTimeout
    ├── HandshakeTimeout
    ├── InvocationCanceled
    └── NegotiationError

SignalRError​

Base class for all aiosignalr errors.

ProtocolError​

A malformed or spec-violating message was received. It is fatal for the connection it occurred on: the client logs it and closes the transport.

HubException​

A hub invocation failed on the remote endpoint.

  • Client: raised by invoke() / stream() when a Completion carries an error (e.g. the hub method raised, or the method does not exist).
  • Server: raise it from a hub method to send a specific error message back to the client (its str() is transmitted verbatim).

ConnectionClosed​

The underlying connection was closed while an operation was in flight.

  • Raised by invoke() / stream() / send() if called while not CONNECTED.
  • Raised when a transport closes unexpectedly and no reconnect policy (or a failed stateful reconnect) can recover the pending call.

ServerTimeout​

The remote endpoint stopped sending messages within the configured server_timeout. The client then closes the connection.

HandshakeTimeout​

The hub handshake did not complete within handshake_timeout.

InvocationCanceled​

An invocation was cancelled before it completed (for example, the connection was stopped mid-call).

NegotiationError​

The POST /negotiate handshake failed (bad status, non-JSON response, server error property, or too many redirects).

Catching errors​

from aiosignalr.errors import ConnectionClosed, HubException, SignalRError

try:
    result = await connection.invoke("add", 1, 2)
except HubException as exc:
    print("the server rejected the call:", exc)
except ConnectionClosed as exc:
    print("the connection was lost:", exc)
except SignalRError as exc:      # catches everything else
    print("some other aiosignalr error:", exc)