export DISPLAY=:0.0 

color codes (see https://www.rapidtables.com/web/color/html-color-codes.html:

• green: rgb(127,255,0)
• yellow: rgb(255,255,0)
• cyan: rgb(0,255,255)
• skyblue: rgb(135,206,235)
• blue: rgb(0,0,255)
• violet: rgb(238,130,238)
• white: rgb(255,255,255)
• lightgray: rgb(211,211,211)
• black: rgb(0,0,0)
• red: rgb(255,0,0)

Idea: creating images on pi and display these images as html files remotely

Use lighttpd as minimal webserver on pi

sudo apt-get install lighttpd 
sudo pip install plotly

Check status

 sudo systemctl status lighttpd 

Set access rights

 
sudo groupadd www-data
sudo usermod -G www-data -a pi
sudo chown -R www-data:www-data /var/www/html
sudo chmod -R 775 /var/www/html
 

restart service

 sudo service lighttpd force-reload 

move html file to be displayed into /var/www/html/

remote browser access html file by:

 http://192.168.1.xx/<filename> 

Only use Python3

 
sudo apt-get install php7.3-cgi php7.3
sudo lighty-enable-mod fastcgi-php
sudo service lighttpd force-reload

php- files in /var/www/html ablegen

Only use Python3

 sudo apt-get install mosquitto mosquitto-clients -y

Paho is needed to call a shell procedure from python. Only availabe under python 3

 pip3 install paho-mqtt 

/etc/rc.local

nohup /home/pi/browserGUI/sensormqtt.py &

import plotly.graph_objects as go
import random

def nextvalue():
    return (random.randint(10,104))

def displayserver():
    while True:
        fig = go.Figure(go.Indicator(
            mode = "gauge+number",
            value = nextvalue(),
            domain = {'x': [0, 1], 'y': [0, 1]},
            title = {'text': "Temperatur"}))

        fig.write_html('/var/www/html/labor.html', auto_open=True)
#fig.show()

#
# Main
# 
if __name__== '__main__':
    try:
        displayserver()
    except KeyboardInterrupt:
        exit()

getlatestvalue.sh

sqlite3 /home/pi/sensor/sensor.db <<END_SQL
.timeout 2000
select ' ',* from latestvalueLabor_A;
END_SQL

python3 thermometer.py `getlatestvalue.sh`