mqtt_publisher example
Example use of the MQTT protocol in KasperskyOS.
In this example, an MQTT subscriber must be started on the host operating system, and an MQTT publisher must be started on KasperskyOS. The Publisher entity is an implementation of an MQTT publisher that publishes the current time with a 5-second interval.
When the example starts and runs successfully, an MQTT subscriber started on the host operating system prints a "received PUBLISH" message with a "datetime" topic.
The example also demonstrates the use of various virtual file systems (VFS) in a single solution. The example uses different VFS to access the functions for working with the file system and functions for working with the network:
VfsNetis used for working with the network.VfsRamfsandVfsSdCardFsare used for working with the file system.
The Env entity is used to pass environment variables and main function arguments to other entities.
The CMake system, which is included with KasperskyOS Community Edition, is used to build and run the example.
Starting Mosquitto
To run this example, a Mosquitto MQTT broker must be installed and started on the host system. To install and start Mosquitto, run the following commands:
$ sudo apt install mosquitto mosquitto-clients
$ sudo /etc/init.d/mosquitto start
To start an MQTT subscriber on the host system, run the following command:
$ mosquitto_sub -d -t "datetime"
Supplied resources
The following configuration files are included in the example:
./resources/include/config.h.incontains a description of the backend file system that will be used in the solution:sdcardorramfs.Each backend in the solution also uses a separate VFS: respectively
VfsSdCardFsorVfsRamfs.- The
./resources/ramfs/etcand/resources/sdcard/etcdirectories contain configuration files for the VFS andNtpdentities.
Example files
The code of the example and build scripts are available at the following path:
/opt/KasperskyOS-Community-Edition-<version>/examples/mqtt_publisher
Building and running example
To run an example on QEMU, go to the directory containing the example, build the example and run the following commands:
$ cd build/einit
# Before running the following command, be sure that the path to
# the directory with the qemu-system-arm executable file is saved in
# the PATH environment variable. If it is not there,
# add it to the PATH variable.
$ qemu-system-arm -m 2048 -machine vexpress-a15 -nographic -monitor none -sd sdcard0.img -kernel kos-qemu-image
See also Building and running examples section.