dnp3-outstation 🐍

Pure-Python DNP3 outstation (IEEE 1815-2012, Level 1 subset).

aarch64-compatible drop-in replacement for the outstation half of dnp3-python, which ships x86_64-only wheels.

Scope (and what's deliberately not in)

✅ One TCP outstation per process, asyncio-native ✅ Group 30 / variation 5 analog inputs (32-bit float with flag byte) ✅ READ requests with qualifier 0x06 (class-0 / integrity poll) and qualifier 0x00 (8-bit range) ✅ Responses encoded as one g30v5 qualifier-0x00 header per contiguous index run (rust dnp3 + opendnp3 accept this) ✅ Datalink REQUEST_LINK_STATUS → LINK_STATUS, RESET_LINK_STATES → ACK ✅ WRITE (FC=0x02) ACKed -- master can clear IIN1.RESTART ✅ IIN1.RESTART on cold start, self-clears after first response ✅ Interop verified against the rust dnp3 v1.6 master crate (same one used by ems-industrial-gateway)

❌ Master mode ❌ Secure authentication (SAv5/SAv6) ❌ File transfer, time sync, control output ❌ Event classes 1/2/3, change-driven reporting ❌ Function codes beyond READ (0x01) and WRITE (0x02)

Anything missing comes from the same place: this lib exists to publish a small, fixed set of analog values to a polling master. That's it.

Install

pip install dnp3-outstation

Python 3.11+, pure-Python — works on any platform Python runs on (Raspberry Pi 5 aarch64 included).

Usage

import asyncio
from dnp3_outstation import AsyncOutstation

async def main():
    outstation = AsyncOutstation(
        host="0.0.0.0",
        port=20000,
        master_addr=1,
        outstation_addr=1024,
    )
    outstation.set_analog(idx=0, value=1_000_000.0)
    outstation.set_analog(idx=1, value=2_000_000.0)
    outstation.set_analog(idx=10, value=250.0)

    await outstation.start()
    try:
        while True:
            # update values on whatever cadence makes sense
            outstation.set_analog(idx=10, value=read_my_sensor())
            await asyncio.sleep(2)
    finally:
        await outstation.shutdown()

asyncio.run(main())

set_analog(idx, value, flag=0x01) updates the in-memory point database. The next master poll returns whatever's there. Flag byte defaults to 0x01 (ONLINE) per the DNP3 analog-input flag definition.

Architecture

Layered to mirror IEEE 1815's stack so each layer tests independently:

   AsyncOutstation     asyncio TCP server, lifecycle
       |
   Outstation          state + orchestration (sync)
       |
   application.py      AC/FC/IIN, g30v5 encoding, READ parsing
       |
   transport.py        FIN/FIR/SEQ segment header
       |
   datalink.py         SYNC + LEN + CTRL + addresses + CRC blocks
       |
   crc.py              CRC-16/DNP per spec section 11.7

Every layer has colocated unit tests under src/dnp3_outstation/test_*.py.

License

MIT.