chumicro-sockets 0.20.0

Cross-runtime TCP + TLS sockets for CircuitPython, MicroPython, and CPython.

chumicro-sockets

One TCP / TLS / UDP socket surface across CircuitPython, MicroPython, and CPython.

One entry per socket shape (connector, listener, udp_socket) hides the per-runtime adapter selection; TLS is a tls= flag on each. Custom-CA TLS, server-side certs, and an in-memory FakeSocket for downstream library tests are all included.

Part of the ChuMicro family — small, focused Python libraries for microcontrollers and laptops. Browse all libraries.

Install

# CircuitPython (after `circup bundle-add ChuMicro/ChuMicro-Bundle`)
circup install chumicro_sockets

# MicroPython
mpremote mip install github:ChuMicro/ChuMicro-Bundle/chumicro_sockets

# CPython
pip install chumicro-sockets

For bundle setup, pre-compiled .mpy bundles, the experimental channel, and details on PyPI naming, see the chumicro INSTALL guide.

Quick example

from chumicro_sockets import connector

# One connect state machine per runtime.  Runner-shaped apps register
# the connector with the runner (it exposes check / handle / io_*);
# one-shot scripts drive it to terminal inline.  On CircuitPython pass
# radio=wifi.radio; the kwarg is ignored on MicroPython / CPython.
dial = connector("broker.example.com", 1883, radio=wifi.radio)
while dial.state not in ("ready", "failed"):
    dial.tick(0)
if dial.state == "failed":
    raise dial.last_error
sock = dial.socket
sock.send(b"PING\r\n")
buffer = bytearray(128)
nbytes = sock.recv_into(buffer, 128)
print(bytes(buffer[:nbytes]))
sock.close()

# TLS is a flag — `tls=True` verifies the cert chain on every runtime.
# Each runtime gets its trust roots from the right place:
# CircuitPython's firmware bundle, CPython's OS trust store,
# MicroPython's library-shipped bundle (override via
# `set_default_ca_bundle`).  Pass `context=ssl_context_no_verify()`
# for explicit opt-out.
dial = connector("api.example.com", 443, tls=True)

CircuitPython always needs an explicit radio= — the socketpool is built from it (socketpool.SocketPool(radio)). Pass wifi.radio, or whatever radio object your board exposes. MicroPython and CPython ignore the kwarg.

For tests, chumicro_sockets.testing.FakeSocket implements the same protocol against in-memory bytearrays so downstream libraries (chumicro-mqtt, future chumicro-requests) can reach 94 % coverage without hitting the network.

What's included

Symbol	Purpose
connector(host, port, *, tls=False, context=None, radio=None)	Non-blocking tick-driven TCP/TLS connect — the one connect state machine. Register it with a runner or drive tick() to terminal inline.
listener(host, port, *, tls=False, context=None, backlog=4, radio=None)	Open a non-blocking TCP or TLS listening socket.
udp_socket(bind_host="0.0.0.0", bind_port=0, *, radio=None, broadcast=False)	Open a UDP datagram socket; default args bind ephemeral.
ssl_context_with_ca(ca_pem)	Build an ssl.SSLContext trusting only the supplied CA(s). Works on every supported runtime.
ssl_context_no_verify()	Build an ssl.SSLContext that skips certificate verification. Explicit opt-out — named so a reviewer can grep for it.
set_default_ca_bundle(pem_bytes)	Replace the CA bundle used by connector(tls=True, context=None) on MicroPython. No-op on CP / CPython. Pass None to revert to the library-shipped bundle.
ssl_context_with_cert_and_key_paths(cert_path, key_path)	Server-side ssl.SSLContext from PEM file paths. CP-portable shape.
TCP socket surface (duck-typed)	send, recv_into, close, setblocking, settimeout. Any object exposing these works; no named Protocol class is exported.
UDP socket surface (duck-typed)	sendto(data, host, port), recvfrom_into(buffer, nbytes=0) -> (n, (host, port)), close, setblocking. Any object exposing these works.
UnsupportedSSLConfigError	Raised when the requested TLS shape isn't supported by the current runtime (e.g. CP's in-memory cert+key).
chumicro_sockets.testing.FakeSocket / FakeUDPSocket	In-memory test doubles covering the full TCP / UDP protocol.

Where this fits

No runtime dependencies. On CircuitPython the caller passes a radio (e.g. wifi.radio, or chumicro-wifi's adapter radio) from which the socketpool is built. Substrate for every networked library that follows: chumicro-requests, chumicro-http-server, chumicro-mqtt, chumicro-websockets, and chumicro-ntp.

Platform support

Works on CPython, MicroPython, and CircuitPython.

Examples

Example	What it shows
tcp_roundtrip.py	Real TCP connect → send → recv → close. Same shape on every runtime; pass radio=wifi.radio on CircuitPython.
tls_with_custom_ca.py	Custom-CA TLS via ssl_context_with_ca. Documents the substrate quirks observed on Pi Pico W mbedTLS in the docstring.
udp_echo_client.py	Board-side UDP echo client — wifi up, send datagram to a host echo server, read echo back, non-blocking. Cross-runtime (CP + MP).

Contributing

Working on chumicro-sockets itself? Clone the mono-repo if you haven't already — the rest of the workflow assumes you're inside that workspace.

pip install -e .[test]
pytest tests/                  # host-side tests
pytest functional_tests/       # on-device tests (needs a board registered in devices.yml)

Register a board before running functional tests: chumicro-workspace add-device <id> --address <port>.

Docs

📖 Stable docs · Experimental docs

Find this library

• PyPI: chumicro-sockets
• Bundle: ChuMicro-Bundle (CircuitPython & MicroPython)
• Experimental bundle: ChuMicro-Bundle-Experimental
• Source: libraries/sockets

License

MIT