libcoapy 2024.12.17

Python module to communicate over the CoAP protocol

libcoapy

libcoapy project enables communication over the CoAP protocol (RFC 7252). The llapi module provides ctypes-based wrappers for the libcoap C library. The libcoapy module uses llapi to provide a high-level class interface to the libcoap functions.

Dependencies:

• libcoap (v4.3.5 or higher is recommended)
• ifaddr (optional, to query all IPs of an interface)
• netifaces (optional alternative to ifaddr)

Status

This project is still in early development. Several functions of the libcoap library are not yet available and existing high-level libcoapy APIs might change in the future.

Portability

libcoapy is a pure python module and the underlying libcoap supports several platforms like Linux, Windows, MacOS and Android. However, libcoap (and hence libcoapy) does not support all features on all platforms and with all possible SSL/TLS libraries.

If you want to use libcoapy with asyncio on platforms without epoll, like Windows, it might be necessary to choose an event loop that supports add_reader(). On Windows you might need to add this to your code before initializing the loop:

if sys.version_info[0] == 3 and sys.version_info[1] >= 8 and sys.platform.startswith('win'):
	asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

Tools

• coap-gui - a small Tkinter-based GUI to interact with a CoAP server
• coarl - a CLI tool that provides a similar interface as curl

Example: client

from libcoapy import *

if len(sys.argv) < 2:
	uri_str = "coap://localhost"
else:
	uri_str = sys.argv[1]

ctx = CoapContext()

session = ctx.newSession(uri_str)

def rx_cb(session, tx_msg, rx_msg, mid):
	print(rx_msg.payload)
	session.ctx.stop_loop()

session.sendMessage(path=".well-known/core", response_callback=rx_cb)

ctx.loop()

Example: server

from libcoapy import *

def echo_handler(resource, session, request, query, response):
	response.payload = request.payload

def time_handler(resource, session, request, query, response):
	import datetime
	now = datetime.datetime.now()
	response.payload = str(now)

ctx = CoapContext()
ctx.addEndpoint("coap://[::]")

time_rs = CoapResource(ctx, "time")
time_rs.addHandler(time_handler)
ctx.addResource(time_rs)

echo_rs = CoapResource(ctx, "echo")
echo_rs.addHandler(echo_handler)
ctx.addResource(echo_rs)

ctx.loop()

More examples can be found in the examples directory.