Find IPv4 address using Python

Project help
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1

Hello,

Does anyone know how to find the Local IPv4 address of the same device, running python code?

I was able to find this on google: socket.gethostbyname(socket.gethostname()). It works on my personal laptop, and returns 192.168.1.130. But returns the following error when ran on a RaspberryPI 3 B+ through the Balena dashboard:

 opencv-test  Traceback (most recent call last):
 opencv-test    File "./main.py", line 51, in <module>
 opencv-test      init()
 opencv-test    File "./main.py", line 39, in init
 opencv-test      ip = socket.gethostbyname(socket.gethostname())
 opencv-test  socket.gaierror: [Errno -5] No address associated with hostname

Does anyone know how to associate the IP address with the hostname, or if there is another way of retrieving the address?

4

Hi there Nate,

There reason that socket.gethostname doesn’t work on a balena device, is because it will run in a container. The container has a UUID as it’s hostname which won’t resolve to a network adapter.

The simplest way to achieve what you want, is to user the balena supervisor API. Here’s how to do it from the shell:

curl -X GET --header "Content-Type:application/json" "$BALENA_SUPERVISOR_ADDRESS/v1/device?apikey=$BALENA_SUPERVISOR_API_KEY"

This will give you the IP amongst some other bits: https://docs.resin.io/reference/supervisor/supervisor-api/ 36
If your application is running multiple containers, you need to add some labels to your docker-compose file: https://docs.resin.io/learn/develop/multicontainer/#labels

To get this into your python app, you can either make the request from the code (using requests, or similar) or you could run the code in a bash script (if that’s your container entrypoint) and put the result into an environment variable which your python can use.

Hope this helps.
Phil

6

Thank you, I was able to add the labels to the docker-compose, and when I run this command:

root@855dda1:/usr/src/app# curl -X GET --header "Content-Type:application/json"     "$BALENA_SUPERVISOR_ADDRESS/v1/device?apikey=$BALENA_SUPERVISOR_API_KEY"

It produces this:

{"api_port":48484,"ip_address":"192.168.1.130","os_version":"balenaOS 2.75.0+rev1","mac_address":"B8:27:EB:88:35:2B B8:27:EB:DD:60:7E","supervisor_version":"12.5.10","update_pending":true,"update_failed":false,"update_downloaded":false,"status":"Idle","download_progress":null}root@855dda1:/usr/src/app#

Which to me indicates that the device IP has made it into the container. I tried print(requests.get("http://127.0.0.1:48484/ip_address").content)and a couple others, but it produces b'Unauthorized'. I am wondering if you would be able to show an example for ether using requests, or the environment variable?

Thank you!

7

Thanks for getting back. Not sure how the local loopback service can access the /ip_address, but one way you can try this out with request is emulate the balena-supervisor request like:

''' Assuming Python 3 and above '''
requests.get(f"{BALENA_SUPERVISOR_ADDRESS}/v1/device?apikey={BALENA_SUPERVISOR_API_KEY}", headers={"content-type":"application/json"})

This should be able to provide you IP and all the above info you got via terminal.

  • Nitish
9

Thank you!

I had to change up the code slightly, but I have put it below.

import requests
import os

bsa = os.getenv('BALENA_SUPERVISOR_ADDRESS')
baak = os.getenv('BALENA_SUPERVISOR_API_KEY')
content = requests.get(bsa + "/v1/device?apikey=" + baak, headers={"content-type":"application/json"}).content

-Nate

11

You might also want to take a look at the ifaddr Python library: