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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 and server-side certificates work the same way on every runtime.


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
# the board radio (with chumicro-wifi, radio=wifi.adapter.radio); the
# kwarg is ignored on MicroPython / CPython.
dial = connector("broker.example.com", 1883, radio=None)
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.adapter.radio from a chumicro-wifi WifiService, 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, chumicro-requests) can exercise their protocol handling 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 (wifi.adapter.radio from a chumicro-wifi WifiService, or any radio object the board exposes) 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 the board radio via 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

Issues, bug reports, and pull requests are welcome, and so is "I ran it on this board and here's what happened", some of the most useful feedback a hardware project can get. Development happens in the ChuMicro repository, whose contributing guide covers setup and the test workflow.

Docs

📖 Stable docs · Experimental docs

Find this library

License

MIT

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