MQTT kdb+ library installation

Requirements

kdb+ ≥ 3.5 64-bit(Linux/MacOS/Windows) and 32-bit ARM
paho.mqtt.c >= 1.3.11
CMake ≥ 3.1 ¹

Installing a release

Ensure MQTT C API (paho.mqtt.c) is installed.
- Linux: Paho MQTT provides a pre-build binary which may be built against a more recent version of glibc that may be available on your system, resulting in an error such as '/lib64/libc.so.6: version GLIBC_2.38' not found. To get around this, build from the paho mqtt library from the source code package. See docker_linux/build_libpaho.sh as an example of how to download and build into a tar.gz` package.
Make the MQTT library available from kdb+:
- Linux: Add the lib directory, which includes include and lib to the LD_LIBRARY_PATH environment variable e.g. if unzipped to /usr/local/Eclipse-Paho-MQTT-C/, run:
```
export LD_LIBRARY_PATH=/usr/local/Eclipse-Paho-MQTT-C/lib/:$LD_LIBRARY_PATH
```
- macOS: Add the lib directory, which includes include and libto the DYLD_LIBRARY_PATH environment variable e.g. if unzipped to /Users/jim/eclipse-paho-mqtt-c/, run:
```
export DYLD_LIBRARY_PATH=/Users/jim/Eclipse-Paho-MQTT-C/lib/:$DYLD_LIBRARY_PATH
```
- Windows: Add paho-mqtt3c.dll and paho-mqtt3cs.dll to the kdb+ directory e.g. C:\q\w64 for 64-bit.
Download the latest release of the MQTT interface from our releases page. To install shared library and q files, use:
```
# Linux/MacOS
./install.sh

# Windows
install.bat
```
or copy mqtt.q to QHOME, then copy mqttkdb.so or mqttkdb.dll into QHOME/[l|m|w]64

Required when building from source ↩