= Node-RED

Node-RED is software ran on Node.js that allows for flow-based visual programming in a browser, to wire together hardware, inputs, and services for Internet of Things (IoT) applications. 

Node-RED can be used with the Gateworks SBCs. 

Typically, Node-RED may actually run on a server machine and the Gateworks SBC acts as a client and talks back to the server. Or, Node-RED can be install on the Gateworks SBC itself.

This wiki page assumes the usage of a Gateworks Venice SBC with the latest kernel (5.10 or newer)

= Install Node-RED on Gateworks SBC 

Installing Node-Red on a Gateworks SBC isn't any different than many other Linux platforms, which instructions are detailed on the internet. 

Doing the below commands will make the Gateworks SBC act as the 'server' 
{{{

    sudo apt-get update
    sudo apt-get install mosquitto #if wanting to use the MQTT protocol to talk to client
    sudo apt-get install nodejs #beware Ubuntu default may be 10.19, and it would be better to use a newer version
    sudo apt-get install npm #get the node package manager
    sudo npm install -g --unsafe-perm node-red #install node-red using npm
    node-red #start the node-red application

Welcome to Node-RED
===================

17 Dec 23:23:34 - [info] Node-RED version: v2.1.4
17 Dec 23:23:34 - [info] Node.js  version: v10.19.0
17 Dec 23:23:34 - [info] Linux 5.15.0-00085-g2ec7c180b810 arm64 LE
17 Dec 23:23:37 - [info] Loading palette nodes
17 Dec 23:23:40 - [info] Settings file  : /root/.node-red/settings.js
17 Dec 23:23:40 - [info] Context store  : 'default' [module=memory]
17 Dec 23:23:40 - [info] User directory : /root/.node-red
17 Dec 23:23:40 - [warn] Projects disabled : editorTheme.projects.enabled=false
17 Dec 23:23:40 - [info] Flows file     : /root/.node-red/flows.json
17 Dec 23:23:40 - [warn] 

---------------------------------------------------------------------
Your flow credentials file is encrypted using a system-generated key.

If the system-generated key is lost for any reason, your credentials
file will not be recoverable, you will have to delete it and re-enter
your credentials.

You should set your own key using the 'credentialSecret' option in
your settings file. Node-RED will then re-encrypt your credentials
file using your chosen key the next time you deploy a change.
---------------------------------------------------------------------

17 Dec 23:23:40 - [info] Server now running at http://127.0.0.1:1880/
17 Dec 23:23:40 - [info] Starting flows
17 Dec 23:23:41 - [info] Started flows
17 Dec 23:23:41 - [info] [mqtt-broker:c44d6461e1d6d8c3] Connected to broker: mqtt://localhost:1883

}}}

Once node-red is running, use a browser to open the node-red gui on port 1880.
 * eg http://122.24.11.93:1880/


* Demo Setup:
 * This demo takes an incoming MQTT message from a client and just prints it out in the debug screen.
 * Use the MQTT input module connected to a debug module ti replicate what is shown in the picture below.
[[Image(nodered.png,600px)]]

= Create a Client on Gateworks SBC
{{{

    sudo apt-get update
    sudo apt-get install python #if wanting to use the MQTT protocol to talk to client
    sudo apt-get install nodejs #beware Ubuntu default may be 10.19, and it would be better to use a newer version

}}}

Then, create a python script (example below) to send MQTT messages from the client SBC to the server SBC.

== Gateworks Python Script to send MQTT Messages

The below is a sample python script to pass MQTT messages from the Gateworks SBC to the Node-Red server (broker). The script will pass the Gateworks SBC temperature as the payload and send it specific to the device's serial number. 

{{{
# Compatible with python 2.* version
import sys
import os.path
import json
import time
import random
import paho.mqtt.client as mqtt
from datetime import datetime

def on_message(client, userdata, message):
 print("message received " ,str(message.payload.decode("utf-8")))
 print("message topic=",message.topic)
 print("message qos=",message.qos)
 print("message retain flag=",message.retain)

def on_connect(client, userdata, rc,a):
 print("Connected with result code "+str(rc))
 # Subscribing in on_connect() means that if we lose the connection and
 # reconnect then subscriptions will be renewed.
 client.subscribe("gateways/id/#")

def main(argv):
 client = mqtt.Client("clientone")
 client.on_connect = on_connect 
 client.on_message = on_message 
 broker = "172.24.33.93"
 client.connect(broker) 
 client.loop_start()
 serialnumber = str(open('/proc/device-tree/serial-number', 'r').read())
 print(serialnumber)
 prefix = "gateways/id/"
 time.sleep(1)
 while True:
    try:
        print("in loop")
	temp = float(open('/sys/class/hwmon/hwmon0/temp1_input', 'r').read().strip())/1000
        prefix = "gateways/id/"
        serialnumber = str(open('/proc/device-tree/serial-number', 'r').read().strip('\x00'))
        topic = prefix + serialnumber
        client.publish(topic,temp,1)
        print("done publishing")

    except Exception as ex:
        print(ex.message)
        sys.exit(0)
    time.sleep(5)


if __name__ == "__main__":
    main(sys.argv)

}}}


== Links & Resources
* [https://nodered.org/]
* [http://www.steves-internet-guide.com/into-mqtt-python-client/] 
* [https://nodejs.org/en/about/releases/]