Unable to get devices list

I have eclipse-mosquitto and ewpe-smart-mqtt setup in their own Docker containers on my Synology NAS. 

Using PuTTY and 'docker exec -it \<container id\> sh' I am able to use the mosquitto_pub and mosquitto_sub commands. Any time I run either of the commands on 'ewpe-smart/devices/list', it doesn't return anything. 