signalr-zero

Zero-dependency Python SignalR JSON hub client.
Pure stdlib · mTLS / PFX support · Auto-reconnect · Thread-safe · Python 3.8+

pip install signalr-zero

Why signalr-zero?

Quick Start

from signalr_zero import SignalRClient

client = SignalRClient(
    url     = "https://hub.example.com",
    hub     = "/events",
    api_key = "YOUR-API-KEY",
)

@client.on("OnMessage")
def handle(data: dict) -> None:
    print(data)

client.run()    # blocks — Ctrl-C to stop

With mTLS (PFX / PKCS12 certificate)

For enterprise APIs that require mutual TLS authentication:

from signalr_zero import SignalRClient

client = SignalRClient(
    url          = "https://api.example.com/service",
    hub          = "/hub",
    api_key      = "YOUR-API-KEY",
    pfx_path     = "/path/to/client.pfx",
    pfx_password = "pfx-passphrase",
    subscribe    = "Subscribe",       # hub method to invoke after connect
    subscribe_args = [],              # arguments for the subscribe call
)

@client.on("OnData")
def on_data(data: dict) -> None:
    print(f"Received: {data}")

@client.on_connect
def connected() -> None:
    print("Connected!")

@client.on_disconnect
def disconnected() -> None:
    print("Disconnected — will auto-reconnect…")

client.run()

Windows note: Use a raw string or forward slashes for pfx_path:

pfx_path = r"C:\certs\client.pfx"      # raw string  ✅
pfx_path = "C:/certs/client.pfx"       # forward slash ✅
pfx_path = "C:\certs\client.pfx"       # backslash — DON'T ❌

With PEM files (alternative to PFX)

client = SignalRClient(
    url      = "https://api.example.com/service",
    hub      = "/hub",
    cert_pem = "/path/to/client.crt",
    key_pem  = "/path/to/client.key",
)

Stop from another thread

import threading, time

def stop_after(seconds):
    time.sleep(seconds)
    client.stop()

threading.Thread(target=stop_after, args=(30,), daemon=True).start()
client.run()

Send a hub invocation

@client.on_connect
def on_connected():
    client.invoke("SendMessage", ["hello", "world"])

Enable logging

import logging
logging.basicConfig(level=logging.INFO)   # or DEBUG for raw frames

All Parameters

System Requirements

How it works

signalr-zero implements the ASP.NET Core SignalR JSON Hub Protocol from scratch using only Python's standard library:

1. Negotiate — POST /hub/negotiate to get a connection token
2. WebSocket — RFC 6455 WebSocket upgrade (pure stdlib)
3. Handshake — {"protocol":"json","version":1} → server ACK
4. Subscribe — optional hub method invocation
5. Receive loop — dispatches messages to @client.on() handlers
6. Ping loop — background thread sends keep-alive pings
7. Reconnect — auto-reconnects with configurable delay

License

MIT © Abhishek Kumar