remote backend

Hello all, i have a running remote backend using http with no problems at all, everything runs smoothly.
Now i need to enable unix sockets, so the remote backend is not connected anymore using http but unix socket.

Nothing has changed beside to listen in the unix socket, meaning im returning exactly the same JSON i return in the http but when i start pdns auth i get this

PDNSException while filling the zone cache: Exception caught when sending: Could not send a message to remote process

right after the initialize call which im answering with {"result":true} as usual.

Same result for 4.7.4 and 4.8.3 , do i need to change anything else since in cannot find in the doc any reference to a different response


thanks in advance