Running simple script in background

[gums]

I'm trying to execute a simple script in Python via my iPhone in order to keep alive a Buffalo NAS drive by sending a magic packet every 3 minutes. The script works well as long as I have the Python app open in the foreground but as soon as it moves to the background it looks like it stops executing and the NAS turns off.

Is this a limitation of iOS rather than the python app(s) I'm using? Running on android via QPython in the background seems to work well

[omz]

This is a limitation/feature of iOS. Apps can only run in the background for a couple of minutes before they're suspended by the system, in order to conserve system resources (and improve battery life).

[ccc]

It would be a nice use case for a Raspberry Pi Zero W ;-)

[gums]

@omz many thanks for the confirmation, i can now stop wasting time trying to figure a workaround on ios and use Android.

[gums]

@ccc I'm presuming you mean in such a way as using something like VNC on the iPhone to connect to the Pi and trigger the python script on the Pi which is connected to the home network?

[ccc]

Either that or maybe even more simply on the Pi just run a script of the form:

import time

while True:  # This minimum viable script runs 24 * 7 * 365
    send_magic_bytes()
    time.sleep(3 * minutes)

[mikael]

I use crontab on Zero W to run a periodical Python script, in my case storing temperature data from several sensors to the cloud.

My Zero W does not have a screen or a keyboard, but development experience was nice anyway with a Pythonista action that uses ssh to dump the script to Pi W and run it.

[kaan191]

Hello,

First post here. But have been quietly admiring all the contributions from some of the heroes of this forum. (@mikael, having particularly a lot of fun with your JSWrapper for webviews! I scrape a lot...).

Anyway, I'm not trying to bring this topic back to life, rather, I'm curious if you @mikael have any example scripts of how you communicated with a remote Raspberry Pi server?

I've just bought a Pi 4 (for my kid, but also for me really) and haven't managed to spend much time with it yet.

The use case I'm trying to explore is whether I can send commands (via Pythonista or some other way) to get scripts to run on a remote Pi device. I have Blink Shell (also a nice app) but as I understand it the session closes when the app closes or is too long in the background, and I need it to keep running.

Warning: I'm very much an amateur in all these matters so forgive me if what I'm asking / saying seems dumb.

[cvp]

@kaan191 Welcome in this marvelous forum full of marvelous guys using this marvelous app.
I wonder if I don't use this word too much 🙄, but ok, wisely.

Anyway, I have also used a Raspberry, before I can connect an USB key on my iPad, and I used SSH to connect Pythonista to my Raspberry. You can launch any command, for instance, I used to eject my USB key, via a command = 'sudo umount /media/pi/....'

[mikael]

@kaan191, good to hear you are having fun! I have been a bit quiet here lately, which just means I have a ”hot Pythonista project” on that takes up most of my time.

See below for the script I used to communicate with my Pi. I have it configured in Pythonista actions in three different modes:

1. Move this file to Pi
2. Move this directory to Pi
3. Run this file on Pi – move the file, run it, and show the output in Pythonista.

#coding: utf-8
import paramiko
import editor, console
import os.path
import sys

console.clear()

local_path = editor.get_path()
remote_path = os.path.basename(local_path)
local_dir_path = os.path.dirname(local_path)
remote_dir_path = local_dir_path.split('/')[-1]

print('Open SSH connection')
s = paramiko.SSHClient()
s.set_missing_host_key_policy(paramiko.AutoAddPolicy())
s.connect(<local IP address>, 22, username=<username>, password=<password>, timeout=4)
sftp = s.open_sftp()

fixed_local_root = None
fixed_remote_root = <target dir under root on Pi>
try:
  sftp.mkdir(fixed_remote_root)
except:
  pass # Ok if already exists

if sys.argv[1] == 'dir':
  print('--- Send directory')

  #sftp.put(local_dir_path, remote_dir_path)
  #parent = os.path.split(local_dir_path)[1]
  prefix_len = len(local_dir_path)
  for walker in os.walk(local_dir_path):
    remote_sftp_path = remote_dir_path +  walker[0][prefix_len:]
    if remote_sftp_path.endswith('/'):
      remote_sftp_path = remote_sftp_path[:-1]
    try:
      pass
      #sftp.mkdir(os.path.join(remotepath, walker[0]))
    except:
      pass
    for file in walker[2]:
      print('put', os.path.join(walker[0],file), remote_sftp_path + '/' + file)
      #sftp.put(os.path.join(walker[0],file),os.path.join(remotepath,walker[0],file))
else:
  print('--- Send file')
  sftp.put(local_path, remote_path)

if sys.argv[1] == 'run':

  print('--- Run it')
  stdin, stdout, stderr = s.exec_command('python3 ' + remote_path)
  
  for line in stdout.readlines():
    print(line.rstrip('\n'))
  
  s.close()
  
  print('--- Done')
  
  for line in stderr.readlines():
    print('ERROR:', line.rstrip('\n'))
    
print('--- Complete')

[kaan191]

Brilliant @mikael thanks so much for sharing.

I'll dig into this and post back if I run into trouble.