This is a simple example demonstrating connecting to an MQTT broker, subscribing and publishing some data. This example uses IDF build system and could be configured to be build and executed:

for any ESP32 family chip
for linux target

How to use example

Hardware Required

To run this example, you need any ESP32 development board or just PC/virtual machine/container running linux operating system.

Host build modes

Linux build is supported in these two modes:

WITH_LWIP=0: Without lwIP component. The project uses linux BSD socket interface to interact with TCP/IP stack. There's no connection phase, we use the host network as users. This mode is often referred to as user-side networking.
WITH_LWIP=1: Including lwIP component, which is added to the list of required components and compiled on host. In this mode, we have to map the host network (linux TCP/IP stack) to the target network (lwip). We use IDF's tapif_io component to create a network interface, which will be used to pass packets to and from the simulated target. Please refer to the README for more details about the host side networking.

Building on linux

Configure linux target

idf.py --preview set-target linux

Build the project with preferred components (with or without lwip)

idf.py -DWITH_LWIP=0 build  # Building without lwip (user networking)
idf.py -DWITH_LWIP=1 build  # Building with lwip (TAP networking)

Run the project

It is possible to run the project elf file directly, or using idf.py monitor target (no need to flash):

idf.py monitor

idf.py -DWITH_LWIP=0 build # Building without lwip (user networking)