Domoticz

Hi All,
I am trying to get a VB prog to turn on/off a dummy switch, I can make the socket connection but Domoticz shows in the log
Error: UNHANDLED PACKET TYPE: FS20 74

My command string being sent,
http://127.0.0.1:8181/json.htm?type=com ... tchcmd=Off

I know I am missing something simple.
any help would be appreciated.

Did you try it in a browser (it should tell you whether the json call works or not)? Anyhow, I don't know about the Domoticz error (looks strange), but the json syntax is not quite correct, try changing dparam -> param