Thanks, that worked.

I have the lights working in Domoticz now.

I'm also trying to get the plugin to work on a raspberry pi running raspbian Jessie, but I am getting stuck at getting a PSK.
after I type in:

>$ coap-client -m post -u "client_identity" -k "MY-GATEWEY-KEY" -e '{"9090":"IKEA"}' "coaps://MY-IP:5684/15011/9063"

I get the following reponse:
> v:1 t ...