Can't read BACnet value directly when device is known (BAC0 fails but BACpypes3/Node-RED succeed)

[billybboy]

I'm attempting to read a BACnet value directly from a known device IP (192.168.226.191) using BAC0 v2025.06.10 (Lite), but the request consistently fails with NoResponseFromController. However, the same operation succeeds using bacpypes3 or Node-RED with identical device configuration .

• Environment
  BAC0 Version: 2025.06.10
  Python Version: 3.10
  Host IP/Subnet: 192.168.225.36/24
  Device IP (target): 192.168.226.191
  Tested on: Linux

import BAC0
import asyncio


address = '192.168.226.191'
host_ip = "192.168.225.36"

async def read_values():
    async with BAC0.start() as b:
        print("BACnet started. Reading devices...")
        res = await b.read(f"{address} analog-value 100151 presentValue")
        print(res)

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

it worked using bacpype3:

Am I doing something incorrectly?

[ChristianTremblay]

Somewhere, you chose to use port 47810...
can you use 47808 ?

[billybboy]

I'm unable to use 47808 port on this host, here are the results on another host(192.168.225.19) using the same code on 47808 port:

• Using BAC0
  
• Using bacpypes3
  

FYI, BAC0 worked after I bypassed this block of code in the Read.py(both read and readMultiple coroutine have similar behavior)

if dic is None:
    _iam = await self.this_application.app.who_is(address=address)
    await self.this_application.app.device_info_cache.set_device_info(_iam[0])
    dic = await self.this_application.app.device_info_cache.get_device_info(
        address
    )
    self.log(f"Device Info Cache : {dic}", level="debug")

[ChristianTremblay]

Your problem is related to the nature of broadcast messages in BACnet.
Your instance of BAC0 is in a different subnet than the controller you are pointing to.

The part of code you removed tries to retrieve information from the controller (target) using who_is. This command is sent using (probably 192.168.225.255, based on your IP/24). This command will not traverse to the other subnet (192.168.226.0/24) without help (often, a BBMD in BACnet).

I'm using info_cache in BAC0.device and I'm relying on the basis that the BACnet network should be configured properly. In this particular case, I understand that it may be annoying.

I'll have a further look at this. Looking up closely to your first screen shot, I also see that the script did make a unicast who_is call to the device... I suspect the answer was a broadcast (maybe an old device, unable to respond with a unicast IAM)...

[billybboy]

Thanks a lot!

[ChristianTremblay]

Also, if you cannot use the port 47808 on this host (because it's already in use maybe?), you can always define another IP address for the same network interface and use this new IP address to define your BACnet instance.

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[WeiTangLau]

I am developing a bacnet connector and planning to deploy on docker. Do you think this will be an issue. I am also facing issue with developing on wsl2 given how udp is not being broadcasted properly on wsl2