curl with MQTT publish-subscribe

# The upcoming curl release enables MQTT support by default
# It still has several limitations, that might be show stoppers in most MQTT environments, but it basically works.
# Major requirement for me is following the server-side security-first directive: at least simple authentication + basic TLS 1.2+ support.
# My conclusion here is to keep using the mosquitto_pub/sub tools, when doing such stuff in a terminal window.
# (and of course to try to support the respective curl contributions ;-))

# 1.) Building curl master 
# - git clone https://github.com/curl/curl.git
# - Follow the guide: https://github.com/curl/curl/blob/master/GIT-INFO
autoreconf -fi
./configure
make
sudo make install

# 2.) Test setup
# - Use the Eclipse MQTT test server (mqtt.eclipse.org:1883)
# - Have an MQTT.fx instance and execute this script: https://gist.github.com/jforge/8a21eef42d35b75db3fad76172c6fbf5
# - Consider the limitations: https://github.com/curl/curl/pull/3514

Subscribe (GET) with curl:

/usr/local/bin/curl mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/lastMovement --output - --trace -

To subscribe with wildcards you need to url encode them (# -> %23, + -> %2B)

/usr/local/bin/curl mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/%2B --output - --trace -
/usr/local/bin/curl mqtt://mqtt.eclipse.org/%23 --output - --trace -


Publish (POST) with curl 

/usr/local/bin/curl -d '{ "value": "scanning" }' mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/runMode --output - --trace -  

/usr/local/bin/curl -d $SOME_PAYLOAD mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/lastMovement --output - --trace -

for n in {1..20}; do /usr/local/bin/curl -d $SOME_PAYLOAD mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/lastMovement --output - --trace -; done

with (see also the script curlMqttPublish.sh in this gist)

SOME_PAYLOAD=$(cat <<-END
  { 
    machineId: "1CY816L0ⓥ3", 
    eventTimestamp: `date +%Y-%m-%dT%H:%M:%S%z`,
    temperature: randomTemp,
    position: {
      X: randomX,
      Y: randomY, 
      Z: randomZ
    }, 
    status: "operational"
END
)

curlMqttPublish.sh

#!/usr/bin/env bash
#
# Publish to MQTT server using curl
#

function getNewRandomFloatingPointNumber() {
  local randomNumber=`printf "%02d.%04d\n" $((RANDOM%100 + 10)) $RANDOM`
  echo $randomNumber
}

for n in {1..20}; do
  RANDOM_TEMP=$(getNewRandomFloatingPointNumber)
  RANDOM_X=$(getNewRandomFloatingPointNumber)
  RANDOM_Y=$(getNewRandomFloatingPointNumber)
  RANDOM_Z=$(getNewRandomFloatingPointNumber)
  SOME_PAYLOAD=$(cat <<-END
    {
      "machineId": "1CY816L0ⓥ3",
      "eventTimestamp": `date +%Y-%m-%dT%H:%M:%S%z`,
      "temperature": $RANDOM_TEMP,
      "position": {
        "X": $RANDOM_X,
        "Y": $RANDOM_Y,
        "Z": $RANDOM_Z
      },
      "status": "operational"
    }
END
)
  /usr/local/bin/curl -d "$SOME_PAYLOAD" mqtt://mqtt.eclipse.org/cybus/machine/1CY816L0ⓥ3/lastMovement --output - --trace -
  sleep 2;
done;