ajumalp

From https://synocommunity.com add http://packages.synocommunity.com to your NAS package sources.
For that, go to NAS->Package Cnter->Click Settings->Package Sources tab.
Then from the community, you can see Mosquitto. Install it. 
After installing, please stop the Mosquitto service before updating configuration. You can start service after changes.
Enable Admin login for Synology
Enable SSH in NAS
Download putty and connect to NAS Server
Login using admin 
Change to root user [sudo -i, {use admin password}]
Find mosquitto.conf file [find / -name mosquitto.conf]