to be able to build anything on MacOS, install Command Line Tools for Xcode using the following command:

xcode-select --install

To successfully build mosquitto, cmake is required. To install cmake, follow along these instructions: https://cmake.org/install/.

First time install:

./bootstrap
make
make install

Updating cmake:

cmake .
make      
make install

git clone --single-branch -b master https://github.com/eclipse/mosquitto.git

cd ./mosquitto

• c-ares (libc-ares-dev on Debian based systems) - disable with `make WITH_SRV=no`
• libuuid (uuid-dev) - disable with `make WITH_UUID=no`
• libwebsockets (libwebsockets-dev) - enable with `make WITH_WEBSOCKETS=yes`
• openssl (libssl-dev on Debian based systems) - disable with `make WITH_TLS=no`

When building with SSL:

export OPENSSL_ROOT_DIR="$HOME_BREW/Cellar/openssl/1.0.2n"
export OPENSSL_INCLUDE_DIR="$HOME_BREW/Cellar/openssl/1.0.2n/include"

Generate makefiles

cmake .

make & install libmosquitto

cd ./lib
make
sudo make install

make & install mosquitto clients

cd ../client
make
sudo make install

In case you screwed up, clean directory

git clean -f -d
git reset --hard

cmake -DWITH_TLS_PSK=OFF -DWITH_TLS=OFF .

Add -DCMAKE_MACOSX_RPATH=ON to cmake command

Download latest archive from https://c-ares.haxx.se

./configure
make
sudo make install