- Available for: Linux, Windows
- Driver Linux: vscpl2drv-mqtt.so
- Driver Windows: vscpl2drv-mqtt.dll
MQTT provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for "machine to machine" messaging such as with low power sensors or mobile devices such as phones, embedded computers or micro controllers like the Arduino. A good example of this is all of the work that Andy Stanford-Clark IBM (one of the originators of MQTT) has done in home monitoring and automation with his twittering house and twittering ferry. The MQTT protocol is now an ISO standard maintained by OASIS.
This driver allow publishing of VSCP events as well as subscribing to VSCP events over mqtt. VSCP provide a lot for IoT functionality than mqtt with it's trasport work and they work very well together. To build and use the driver you need yo install the Mosquitto library. You can find instruction on how to do that here.
VSCP daemon driver config
The VSCP daemon configuration is (normally) located at /etc/vscp/vscpd.conf. To use the vscpl2drv-mqtt.so driver there must be an entry in the
> <level2driver enable="true">
section on the following format
<!-- Level II automation --> <driver enable="true" name="link" path-driver="/usr/lib/vscpl2drv-mqtt.so" path-config="/var/lib/vscpl2drv-mqtt/drv.conf" guid="FF:FF:FF:FF:FF:FF:FF:FC:88:99:AA:BB:CC:DD:EE:FF" </driver>
Set enable to "true" if the driver should be loaded.
This is the name of the driver. Used when referring to it in different interfaces.
This is the path to the driver. If you install from a Debian package this will be /usr/bin/vscpl2drv-mqtt.so and if you build and install the driver yourself it will be /usr/local/bin/vscpl2drv-mqtt.so or a custom location if you configured that.
All level II drivers must have a unique GUID. There is many ways to obtain this GUID, Read more here.
vscpl2drv-mqtt driver config
<config debug="true|false" access="rw" keepalive="true|false" sub-filter="incoming-filter" sub-mask="incoming-mask" pub-filter="incoming-filter" pub-mask="incoming-mask" index="index identifying this driver" zone="zone identifying this driver" subzone="subzone identifying this driver" sessionid="" type="subscribe|publish" topic="mqtt path" prefix="mqtt part prefix" remote-host="" remote-port="" remote-user="" remote-password="" <simple enable="true|false" vscpclass="" vscptype="" coding="" unit="" sensoridenx="" index="" zone="" subzone="" /> </config>
Set to 'true' to get debug information written to syslog. Default is 'false' and no debug information written.
Access tells what the driver can do with it's own configuration file.
A 'r' in the access string makes it possible to load a configurations file when the driver is live with the HLO 'load' command.
A 'w' in the access string makes it possible to write a configurations file when the driver is live with the HLO 'save' command.
So an access string "rw" will allow both load and save of a configuration file. While "r" only allow read and "w" only allow write.
If keepalive is set to zero a lost connection to the remote MQTT broker will disconnect forever. If keepalive is set to a value this value is the time in seconds the driver will wait until it tries to reconnect to the remote mqtt broker.
Event filter that together with the rx-mask control which events should be received from the remote mqtt broker.
Can be used to limit the events that is recived on a subscribe channel.
Event mask that together with the rx-filter control which events should be received from the remote mqtt broker.
Can be used to limit the events that is recived on a subscribe channel.
Event filter that together with the tx-mask control which events should be sent to the remote mqtt broker.
Can be used to limit the events that is transmitted on a publishing channel.
Event mask that together with the tx-filter control which events should be sent to the remote mqtt broker.
Can be used to limit the events that is transmitted on a publishing channel.
This is the index used for events originating from the driver itself. A typical example is the CLASS1.INFORMATION, Type=6, Node Heartbeat the driver send every minute.
This is the zone used for events originating from the driver itself. A typical example is the CLASS1.INFORMATION, Type=6, Node Heartbeat the driver send every minute.
This is the subzone used for events originating from the driver itself. A typical example is the CLASS1.INFORMATION, Type=6, Node Heartbeat the driver send every minute.
This is a string that identify this client session. The first configuration parameter is a unique id like "mysession22" for your connection.
This value should either be 'subscribe', which also is default, or 'publish'. A subscribe connection get events from a remote mqtt broker. A publish connection send events to a remote mqtt broker.
This is the topic string used for subscribing pr publishing.
The default subscribing topic is
This will receive all events that uis posten to topic /vscp and all subtopics for this level. That is events published on /vscp/guid/class and /vscp/guid/class/type will be received.
The default publishing topic (if topic is empty) is
where guid/class/type will be set to the guid, class and type of the published event.
If set that topic will be used. That is no guid's, class, type will be added to the topic string on send.
Prefix is a string used in front of any configured topic. This prefix is also prepended to an empty topic string.
This the address for the remote mqtt broker.
This is the port used for connections on the remote mqtt broker. Default is 1883 for a non-tls connection and 8883 for a tls connection.
This is the username needed to connect to the remote mqtt broker. If left empty no username/passord will be used.
This is the password needed to connect to the remote mqtt broker.
path to a file containing the PEM encoded trusted CA certificate files. Either cafile or capath must not be NULL.
path to a directory containing the PEM encoded trusted CA certificate files. See mosquitto.conf for more details on configuring this directory. Either cafile or capath must not be NULL.
path to a file containing the PEM encoded certificate file for this client. If NULL, keyfile must also be NULL and no client certificate will be used.
path to a file containing the PEM encoded private key for this client. If NULL, certfile must also be NULL and no client certificate will be used.
The simple tag is used to configure parameters for the simple connection mode of the driver which can be used for VSCP measurement events. All other event types will be ignored when enabled.
In the simple mode pure measurement values are sent instead of evnets for both subscribe and publish modes.
Simple mode will be used if set to 'true'- Simple mode will not be used if set to 'false'.
This is the VSCP class that should be used to generate the measurement value from. It can be any of the measurement classes.
This is the VSCP tyoe of the VSCO class that should be used to generate the measurement value from. It can be any of the types from a measurement classes.
Not used at the moment
This is the unit the measurement event should have. If it has another unit it will be thrown away. Default is zero.
This is the sensorindex the measurement event should have. If it has another sensorindex it will be thrown away. Default is zero.
This is the index the measurement event should have. If it has another index it will be thrown away. For a measurement class that does not use an index it is not used. Default is zero.
This is the zone the measurement event should have. If it has another zone it will be thrown away. For a measurement class that does not use an zone it is not used. Default is zero.
This is the subzone the measurement event should have. If it has another subzone it will be thrown away. For a measurement class that does not use an subzone it is not used. Default is zero.
Install the driver on Linux
You can install the driver using the debian package with
sudo dpkg -i vscpl2drv-mqtt
the driver will be installed to /usr/lib
After installing the driver you need to add it to the vscpd.conf file (/etc/vscp/vscpd.conf). Se the configuration section above.
You also need to set up a configuration file for the driver. If you don't need to dynamically edit the content of this file a good and safe location for it is in the /etc/vscp/ folder alongside the VSCP daemon configuration file.
If you need to do dynamic configuration we recommend that you create the file in the /var/vscp/vscpl2drv-mqtt
A sample configuration file is make available in /usr/share/vscpl2drv-mqtt during installation.
Install the driver on Windows
How to build the driver on Linux
To build this driver you have to first install the vscp common code. You do this with
In your .bashrc you then need to add the path to the location where the common code is located. Add
Now clone the driver source
git clone https://github.com/grodansparadis/vscpl2drv-mqtt.git cd vscpl2drv-mqtt ./configure make make install
Default install folder is /usr/lib
You need build-essentials and git installed on your system
sudo apt update && sudo apt -y upgrade
sudo apt install build-essential git
How to build the driver on Windows
|_sessionid||string||A unique session id ("myconnection2") you set for every connection to a broker. The session id's must be different if load several MQTT drivers and also so if the connect to the same broker. Available from version 188.8.131.52 Sodium.|
|_type||string||“subscribe” to subscribe to a MQTT topic. ”publish” to publish events to a MQTT topic. Defaults to “subscribe”.|
|_topic||string||This is a text string identifying the topic. It is recommended that this string starts with “vscp/”. Defaults to “vscp”|
|_host||string||IP address or a DNS resolvable address to the remote host. Mandatory and must be declared either in the configuration string or in this variable. Note that port must be included in the hostname. Defaults to “localhost:1883”|
|_user||string||Username used to log in on the remote MQTT sever. Defaults to empty. Currently not used.|
|_password||string||Password used to login on the remote MQTT server. Defaults to empty. Currently not used.|
|_keepalive||integer||Keepalive value for channel. Defaults to 60.|
|_filter||string||Standard VSCP filter in string form. 1,0x0000,0x0006,ff:ff:ff:ff:ff:ff:ff:01:00:00:00:00:00:00:00:00 as priority,class,type,GUID Used to filter what events that is received from the socketcan interface. If not give all events are received/sent.|
|_mask||string||Standard VSCP mask in string form. 1,0x0000,0x0006,ff:ff:ff:ff:ff:ff:ff:01:00:00:00:00:00:00:00:00 as priority,class,type,GUID Used to filter what events that is received from the socketcan interface. If not give all events are received/sent.|
|_simplify||string||Makes it possible to publish and subscribe data in a human handleable form. See below for more information.|
The full variable name is built from the name you give the driver (prefix before _variablename) in vscpd.conf. So in the examples below the driver have the name mqtt1 and the full variable name for the _sessionid will thus be
If you have another driver and name it mqtt2 it will therefore instead request variable
and so on.
If your driver name contains spaces, for example “name of driver” it will get a prefix that is “name_of_driver”. Leading and trailing spaces will be removed.
If this variable is defined it will simplify the effort to publish measurement or subscribe to measurement information. It makes it as simple as 1-2-3 and allows for sending just numbers over MQTT but still get valid events into the system. The functionality works also the other way around so measurement events can send data over MQTT as just a number possibly using the MQTT topic as a way to tell what is sent.
For a publishing channel it may be wise to set a filter in the driver so only the events of interest is published.
The format for the simplicity variable varies for the VSCP class one want to use
Only string and float coding is allowed. For string the number can be a maximum of seven characters.
The variable format is
10, vscp-type,float|string, sensoridx(0-7), unit(0-7)
(VSCP types are here) so if you code a simplify variable as
for a subscribe setup a number like "23.78" send over MQTT will be converted to a valid VSCP event CLASS1.MEASUREMENT, Type=6, temperature and with unit set to degrees Celsius and sensor index set to 2 and where the data is a single precision floating point number (32-bit). The setup is of course the same for a publish setup. The GUID for the interface will be used.
If you select a float or a string is just a matter of preference in most cases but the floating point value is often the best choice.
If you need a floating point value with more precision this is the choice. It uses a double (64-bit) double precision floating point number.
The variable format is
1060, vscp-type, sensoridx(0-255), unit(0-255), zone(0-255), subzone(0-255)
This measurement format allow for a decimal measurement ("." is decimal separator) which allow for a maximum of 483 digits including a possible decimal point. So if you need a lot of numbers this is the format for you.
The variable format is
1040, vscp-type, sensoridx(0-255), unit(0-255), zone(0-255), subzone(0-255)
<driver enable="true" > <name>mqtt1`</name> <path>/usr/local/lib/vscp2drv_mqtt.so</path> <config>"mysession1";publish;vscp;localhost:1883</config> <guid>`00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00</guid> </driver>
The format for data on the MQTT wire is the same as the format for sends and receives in the TCP/IP interface. This means they look like this
and as usual the GUID can be replaced by “-” to use the interface GUID.
Using the methods
available in the vscphelper library (C/C++/C#/Python/PHP/node.js) it is easy to convert between VSCP Event and text form. It is also very easy to get other properties from the event such as real number measurement with the help of the same library.
Using the MQTT driver
MQTT is a protocol for M2M by IBM. This driver makes it possible to use MQTT as the transport for VSCP events. As MQTT, with the help of IBM's muscle mass, is available on many, many platforms this can be a way to enter events into or fetch events from the VSCP framework. Thus any device that can use MQTT can connect to a websocket button or show it's data in a table or log data to a database.
For measurements it be as easy as 1-2-3. You just send or fetch data and the driver do the VSCP translations to full events for you.
Setting up the needed MQTT subsystem
This has been tested on several Debian and Ubuntu boxes and on a Rasbian driven Raspberry Pi board. On all I tested you can jump directly to step 4. If that does not work start at step 1.
Install a MQTT broker and a client
Install the Mosquitto server and clients
$ sudo apt install mosquitto $ sudo apt install mosquitto-clients
You are now ready to use the MQTT subsystem.
To test that everything works you can now open a terminal window and issue
$ mosquitto_sub -d -t hello/world
to subscribe to the hello/world channel. And then open another terminal window and issue
$ mosquitto_pub -d -t hello/world -m "Hello World"
if everything works "Hello World" will come up in the subscribe window. You can of course do this on different machines also. On one machine issue
$ mosquitto_sub -h YOUR_HOST_IP_ADDRESS -d -t hello/world
and on the other issue
$ mosquitto_pub -d -t hello/world -m "Hello World"
as before. If this does not work you may need to open the 1883 port in your firewall. For this use
sudo iptables -A INPUT -p tcp -m tcp --dport 1883 -j ACCEPT
Setting up the MQTT driver
You can find the documentation for the driver here
The first thing you should do is to add the driver to the VSCP daemon configuration file. To do this look up the
</vscpdriver> tags in the file and add
<driver enable="true"> <name>VSCP MQTT Publisher driver 1</name> <path>/usr/local/lib/vscpl2drv_mqtt.so</path> <config>mysession2;publish;vscp;localhost:1883</config> <guid>00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00`</guid> </driver>`
Select a name that works for you. enable should be set to true for the driver to be loaded and to false if not. This can be convenient if you want to have a driver in the configuration file but not want to enable it.
The path may be different on your system but /usr/local/bin is the default installation path on most systems. Replace with the correct path if its different on your system.
GUID is all set no zeros here which means the GUID of the interface will be used. You can leave it out if you want to give the same effect or you can set it to a unique id.
The config item tells how your driver should work. It is a semicolon separated list with items that is fully described in the specification document.
The first item in this list can be subscribe or publish depending if you want VSCP events to be sent or received, publish is used in this example as we want to publish events.
The second is the the topic. This is the MQTT term for a channel and is a slash separated list. You can use anything here but staring your topic with vscp is recommended. We use vscp here but could have used vscp/measurements/temperature/celsius or something similar instead. Use the topic that works for you.
Next is the host where your Mosquitto daemon is installed (defaults to "localhost:1883") and must include the port and the host is followed by an optional username and password.
To this list you can add a keepalive value which is the number of seconds the server expect to be feed with messages (Defaults to one minute) and a usual event filter/mask pair to select which events should be published or be received.
Restart the daemon with
$ sudo /etc/init.d/vscpd restart
and subscribe to the published events with
$ mosquitto_sub -d -t vscp
Events is presented in the form
by default (this can be changed see below). You can use the helper library and the methods
to easily interpret the event.
You can easily control that the driver is loaded by using the internal web interface of the daemon and open
with your actual host and port. This will show something like this
where the driver with the name you given it will be visible in the list.
To subscribe to events on a channel use subscribe instead of publish above.
<driver enable="true" > <name>VSCP MQTT Subscriber driver 1</name> <path>/usr/local/lib/vscp2drv_mqtt.so</path> <config>subscribe;vscp;localhost:1883</config> <guid>00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00</guid> </driver>
When the server is restarted and the driver is loaded you can publish VSCP events with
$ mosquitto_pub -d -t vscp -m "0,20,3,0,0,0:1:2:3:4:5:6:7:8:9:10:11:12:13:14:15,0,1,35"
$ mosquitto_pub -d -t vscp -m "0,20,3,0,0,-,0,1,35"
both of these will publish the VSCP event CLASS1.INFORMATION TYPE=3 ON event, for zone=1, sub-zone=35 typically used to tell that something has been turned on in zone=1, subzone=35. In the first case a specific GUID is used (0:1:2:3:4:5:6:7:8:9:10:11:12:13:14:15) and in the second the GUID of the interface has been used. You can use the interface GUID also by specifying the GUID to all nills (00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00) as always.
Use VSCP Works to examine published events received by the MQTT driver in a user friendly way or telnet to the TCP/IP interface of the daemon
$ telnet localhost 9598
$ user admin $ pass secret
works on a newly installed system with the default configuration. Otherwise replace with your own credentials and also the host you have the daemon on of course if your not located at the same host.
to retrieve one event from the input queue
$ retr 25
if you want to fetch 25 or all that is collected. You can also use
to see incoming events (use 'quitloop' to terminate the loop). The "+OK" you may see from time to time is a way for M2M routines to know the line is open as this is intended for machines.
In both cases events will be presented as
All command of the daemon is described here.
Using remote variables
The configure string in the VSCP daemon driver configuration can be replaced by VSCP variables instead. Actually a value specified in a variable will be used before a value in a configuration string. So if you have both the variable value will have precedence.
All the variables for the MQTT driver is defined here. There is one each for the configuration values defined above.
There is _type which in our case is the variable vscp_mqtt_publisher_driver_1_type and vscp_mqtt_subscriber_driver_1_type. As you see the driver name is prepended to the variable name (with spaces replaced by "_") to get the actual variable name. This method makes it possible to have several channels open at the same time with different configurations as long as they have different names. The _type variable can have the value "subscribe" or "publish" and is a variable of string type.
You can create a variable in two ways.
Either you add them by hand to the variables configuration file in /etc/vscp/variables.xml. So in this case you enter
<variable type="string" > <name>vscp_mqtt_publisher_driver_1_type</name> <value>publish</value> <note>bla bla bla bla</note> </variable>
<variable type="string" > <name>vscp_mqtt_subscriber_driver_1_type</name> <value>subscribe</value> <note>bla bla bla bla</note> </variable>
but is is probably easier to use the built in web interface of the daemon to do the same thing. Head your browser to
replacing http://localhost:8884 with your actual host and port.
In this first screen you select the value to be a string and then move on with the next button \
In the next screen you enter the name and the value for the variable as you did above and also make sure to mark persistent so the variable will be saved and thus available also after the daemon has been restarted. When you are ready press save
which will take you back to the variable list where you can click on any item to edit it.
If you enter a driver entry like this in the /etc/vscp/vscpd.conf file
<driver enable="true" > <name>VSCPMQTTDriver1</name> <path>/usr/local/lib/vscp2drv_mqtt.so</path> <config>mysession3;publish;vscp1;localhost:1883</config> <guid>00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00</guid> </driver>
you can subscribe to the events published using
mosquitto_sub -d -t vscp1
And if for instance you have a temperature sensor in your system you will get events looking like this
This is the textual representation of a VSCP event. It has the form
The GUID (always presented in hexadecimal) tells from which interface or device/sensor this event comes from. It as all data in VSCP comes with the MSB byte first.
class and type is the event class and the event type, In this case class=10 so we know its a CLASS1.MEAUREMENT and type=6 so we can tell this is a measurement of a temperature. CLASS1.MEAUREMENT gives information about how the data that follows is packed. As we see there is two databytes 0x68 and 0x44. For CLASS1.MEAUREMENT the first byte of the data is a data coding byte which tells how the rest of the data is coded in the upper three bits. In this case 0x68 = 01101000 the upper bits are 011 which says an integer follows. An integer that can take up 1-7 byte with the most significant byte first. In this case our integer is juts one byte.
So what we have is the temperature 0x44 which is 68 in decimal. But in what unit is it presented? To know that we can investigate bit 3 and 4 which are 01 which in turns tell us that it is a temperature reading in Celsius. It could have been 00 for a Kelvin reading or 10 for a Fahrenheit reading.
The lowest three bits are all zero here but could have been an index (0-7) to a specific sensor on the device that is identified by GUID
More to read
- Using the VSCP MQTT driver Part 1
- Using the VSCP MQTT driver Part 2
- MQ Telemetry Transport - https://mqtt.org/
- MQTT V3.1 Protocol Specification - https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#keep-alive-timer
- Mosquitto - https://mosquitto.org/
- Using the API - https://www.eclipse.org/paho/files/mqttdoc/Cclient/
- MQTT på arduino - https://knolleary.net/arduino-client-for-mqtt/
Copyright (C) 2000-2020 Ake Hedman, Grodans Paradis AB - MIT license.