MQTT

PVLng can listen to a MQTT broker running on any server.

MQTT is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. -- MQTT

PVLng scripts can send to any MQTT broker.

Setup your own mosquitto broker

sudo apt-get update
sudo apt-get install mosquitto

If you run the PVLng scripts also on this host or on remote equipment running the scripts only you need only the clients scripts

sudo apt-get update
sudo apt-get install mosquitto-clients

Configure MQTT broker

Put the following into /etc/mosquitto/conf.d/local.conf

cat <<EOT | sudo tee /etc/mosquitto/conf.d/local.conf
log_type error
log_type warning
log_type notice
log_type information
connection_messages true
log_timestamp true
EOT

And restart

sudo /etc/init.d/mosquitto restart

Test your broker best with 2 terminals

Terminal 1 - Start subscriber

Wait for 1 message, print verbose message and exit

# mosquitto_sub -d -v -i test-subscriber -t test -c -C 1
Client test-subscriber sending CONNECT
Client test-subscriber received CONNACK
Client test-subscriber sending SUBSCRIBE (Mid: 1, Topic: test, QoS: 0)
Client test-subscriber received SUBACK
Subscribed (mid: 1): 0

Terminal 2 - Publish a zero length test message

# mosquitto_pub -d -n -i test-publisher -h localhost -t test
Client test-publisher sending CONNECT
Client test-publisher received CONNACK
Client test-publisher sending PUBLISH (d0, q0, r0, m1, 'test', ... (0 bytes))
Client test-publisher sending DISCONNECT

Terminal 1 - Received the message?

...
Client test-subscriber received PUBLISH (d0, q0, r0, m0, 'test', ... (0 bytes))
test (null)
Client test-subscriber sending DISCONNECT

Run PVLng MQTT subscriber

The script is tools/mqtt-subscribe.sh

Start it at reboot via cron

cat <<EOT | sudo tee /etc/cron.d/mqtt-subscribe
# MQTT listener, wait for mosquitto broker
@reboot root sleep 60 && /path/to/PVLng/tools/mqtt-subscribe.sh start >/dev/null
# And check at least each hour
0 * * * * root /path/to/PVLng/tools/mqtt-subscribe.sh start >/dev/null
EOT

Check for safety reasons each hour.

To store data into PVLng database send a message to topic

pvlng/<API key>/data/<Channel GUID>

Configure PVLng scripts

The scripts check for configured MQTT broker and use it, otherwise the default curl method is used as before.

You need only set the MQTT broker in PVLng.conf and uncomment the line.

##############################################################################
### Send to mosquitto broker running on $mosquittoServer
##############################################################################
### <Sever>[:<port>]
#mosquittoServer=$PVLngDomain:1883

If you test your scripts and send data, you can watch the stream in a terminal with

mosquitto_sub -v -t pvlng/+/data/#

This will give you something like this (2 temperature sensors)

pvlng/df9adc61-e81b-1e12-8fc7-8a1f000a3025/data/72f9-9c42-36c5-c2af-3c01-cd95-67a1-98d1 {"data":"29.5","timestamp":"1495051260"}
pvlng/df9adc61-e81b-1e12-8fc7-8a1f000a3025/data/bef9-6e8b-29a1-15a3-4100-58d2-69b8-3bdb {"data":"24.1875","timestamp":"1495051260"}