aiocoap

0.4.17 verified Mon Apr 27 auth: no python

aiocoap is a Python library for the Constrained Application Protocol (CoAP) as defined in RFC 7252. Current version 0.4.17 supports Python >=3.10. It provides both client and server abstractions with async/await support. Releases are semi-regular, with major version changes introducing breaking API shifts.

pip install aiocoap

Common errors

error ImportError: cannot import name 'Message' from 'aiocoap' ↓

cause Old import path from aiocoap.message import Message used in code written for aiocoap <0.4.

fix

Change to 'from aiocoap import Message'.

error aiocoap.error.FeatureNotImplementedError: DTLS support requires module 'tinydtls' ↓

cause Trying to use coaps:// URIs without installing DTLS support.

fix

Install aiocoap with DTLS extras: pip install aiocoap[dtls] or install tinydtls manually.

error AttributeError: 'EventLoop' object has no attribute 'run_until_complete' ↓

cause Using deprecated loop-based pattern in Python 3.10+ where asyncio.get_event_loop() may return a different loop type.

fix

Use asyncio.run(main()) or Context.create_client_context() as async context manager.

Warnings

breaking aiocoap 0.4 introduced major API changes: import paths moved from submodules to top-level (e.g., from aiocoap import Message instead of aiocoap.message.Message). Context creation changed: use Context.create_client_context() instead of old patterns asyncio.get_event_loop(). Code written for 0.3.x will not work. ↓

fix Update imports to use top-level names and use the new Context API.

deprecated The async context manager pattern (async with Context.create_client_context()) is now preferred over the old loop-based pattern. Old code using loop.run_until_complete may still work but is deprecated. ↓

fix Use 'async with Context.create_client_context() as context:' to ensure proper resource cleanup.

gotcha CoAP URIs must start with 'coap://' or 'coaps://' (for DTLS). Using 'http://' will cause a silent malformed URI error. ↓

fix Always verify the URI scheme is correct for CoAP.

gotcha When sending large payloads (> 64 KiB), aiocoap requires block-wise transfer (Block1/Block2). Without explicit block options, the library may fail with a MessageTooLong error. ↓

fix Use 'from aiocoap import BlockOption' and set appropriate block options on the request.

Imports

Message
wrong
```
from aiocoap.message import Message
```
correct
```
from aiocoap import Message
```
In older versions (pre-0.4), the module path was different. Use top-level import.
Context
wrong
```
from aiocoap.protocol import Context
```
correct
```
from aiocoap import Context
```
Context moved to top-level in 0.4. Old import path breaks.
GET
wrong
```
from aiocoap.numbers import GET
```
correct
```
from aiocoap import GET
```
In 0.4, request codes are directly under aiocoap.
POST
```
from aiocoap import POST
```
PUT
```
from aiocoap import PUT
```
DELETE
```
from aiocoap import DELETE
```

Quickstart

Minimal CoAP client that fetches the resource discovery from coap.me.

import asyncio
from aiocoap import *

async def main():
    context = await Context.create_client_context()
    request = Message(code=GET, uri='coap://coap.me/.well-known/core')
    response = await context.request(request).response
    print(response.payload.decode())

if __name__ == "__main__":
    asyncio.run(main())