I have a PC that transmits log data over a TCP/IP socket to a Raspberry Pi. I have written a python server program that runs on the Pi, so that when certain keywords are encountered, it has to play the corresponding audio track - this is a gist of the problem I'm currently working on.
Now, I want this server program to run as soon as the Raspberry Pi boots up, and so I wrote a systemd service to enable that. Assuming my server code is named as server.py, my service file looks as follows:
[Unit]
Description=Python Server
[Service]
# Command to execute when the service is started
ExecStart=/usr/bin/python3 -u /usr/bin/server.py
[Install]
WantedBy=multi-user.target
I make this server program executable, and I don't face any issues to start and enable the service (verified by rebooting the Pi as well). Now, taking a step back, I play the audio track on the python server program using the following lines (a little snippet):
import subprocess
subprocess.run(["cvlc", "~/Downloads/doors.wav"])
No errors here, all good. But when the service that runs the server program is started, when the specific keyword is encountered, the audio track does not play - it shows an error:
: [00005565470df480] vlcpulse audio output error: PulseAudio server connection failure: Connection refused
: [0000556547157310] dbus interface error: Failed to connect to the D-Bus session daemon: Unable to autolaunch a dbus-daemon without a $D
: [0000556547157310] main interface error: no suitable interface module
: [000055654700c570] main libvlc error: interface "dbus,none" initialization failed
: [0000556547101460] main interface error: no suitable interface module
: [000055654700c570] main libvlc error: interface "globalhotkeys,none" initialization failed
: [0000556547101460] dummy interface: using the dummy interface module...
: [00007f5f98c0b610] idummy demux: command `quit'
This same error shown above occurs when I try to play the audio from the command line with sudo, that is:
cvlc ~/Downloads/doors.wav
which led me to believe that if the service is enabled, then the whole python program corresponding to the service is run with sudo privileges automatically, even if I don't intend that to happen. I did a little bit of digging, but based on what I understand, to run the service, sudo privilege is necessary. I was not able to find a solution to run vlc with sudo, although I understand that ideally sudo privileges should not be given to something such as vlc. Is there a way around this?