Unable to access pi camera through web browser

Question

I am writing a Python CGI script that I want to run on my laptop's browser. This script will SSH into two Pis, and give the command to take a photo. The server hosting this script is on one of the Pis that I want to SSH into, and that Pi also is acting as an access point for the other Pi and my laptop to connect to (everything is a LAN, not connected to the Internet).

I am successfully able to run this script on my laptop's browser to run simple commands like ls -l on both Pis and print out the results for both on the browser. But, I ultimately want to be able to give the raspistill command to both Pis. When I do this, only the Pi with the server is taking the image, but the other Pi is not. I assume it's because permissions aren't set properly for the server (I tried running the commands as sudo but still no luck). However, if I run the same script on a Python IDLE it works fine. Can somebody help me identify the issue?

Here is my script:

#! /usr/bin/env python3

from pssh import ParallelSSHClient
import cgi

print("Content-Type: text/plain\r\n")
print("\r\n ")

host = ['172.24.1.1','172.24.1.112']
user = 'XXXX'
password = 'XXXX'
client = ParallelSSHClient(host, user, password)

output = client.run_command('raspistill -o test.jpg', sudo=True)

// AMENDMENT:
for line in output['172.24.1.1'].stdout:  // works as well with '172.24.1.112'
    print(line)

AMENDMENT: Apparently, if I output anything from the stdout it works fine. Why is this the case? Is is just waiting for me flush the output or something? I suspect this might be a issue with the pssh package I am using.

Answer 1

After thoroughly reading through the documentation for the pssh module, my problem had to do with the exit codes and how they are handled.

The documentation about run_command states that:

function will return after connection and authentication establishment and after commands have been sent to successfully established SSH channels.

And as a result:

Because of this, exit codes will not be immediately available even for commands that exit immediately.

Initially, I was just blindly running the run_command expecting the commands to finish, but it turns out I need to get the exit codes to truly finish the processes the commands are running. The documentations states a couple of ways to do this:

At least one of

• Iterating over stdout/stderr to completion
• Calling client.join(output) is necessary to cause parallel-ssh to wait for commands to finish and be able to gather exit codes.

This is why in my amendment to the code, where I was outputting from stdout, the commands seemed to work properly.

Answer 2

In your pi, go into the terminal and type sudo raspi-config and then navigate with the keys to camera and then enable it. This will restart you pi. From https://www.raspberrypi.org/documentation/configuration/camera.md:

Use the cursor keys to move to the camera option, and select 'enable'. On exiting raspi-config, it will ask to reboot. The enable option will ensure that on reboot the correct GPU firmware will be running with the camera driver and tuning, and the GPU memory split is sufficient to allow the camera to acquire enough memory to run correctly.

After this, go into sudo raspi-config and enable ssh (which is another option just like pi-camera). Link for this here