These directories provide the source code examples that show how to use the various APIs. To build and run these source files on a supported platform you need to travel down into the port/platform/<platform>/mcu/<mcu> directory of your choice and follow the instructions in the README.md there. For instance to build the examples on an ESP32 chip you would go to port/platform/esp-idf/mcu/esp32 and follow the instructions in the README.md there to both install the Espressif development environment and build/run the examples.
For each MCU you will find a runner build. This builds and runs all of these examples and all of the unit tests.
- sockets contains examples of how to bring up a network (cellular or Wi-Fi) and use it to make a UDP or TCP socket connection to a server on the public internet.
- security contains examples of how to use the u-blox security features.
- location contains examples of how to get a location fix.
- mqtt_client contains an example of how to use the MQTT client API to contact an MQTT broker on the public internet.
- cell contains examples specific to u-blox cellular modules (e.g. SARA-U201, SARA-R4 or SARA-R5).
- utilities/c030_module_fw_update is not so much an example as a program that is required if you need to update the firmware of the cellular module on a C030-R5 or C030-R4xx board.