wifi signalK display

[cepicscepics]

Hi, I installed the signalk-mqtt-gw plug-in, but "Provider & Plugin Status" give me an error:

Failed to start: /home/pi/.signalk/node_modules/mdns/build/Release/dns_sd_bindin...

and I can't enable and configure it.

I'm trying to send simulated signalK from Signal K delta simulator...

on esp8266 side, I'm following this how to, to receive playload. (I really don't know ESPEasy) 
I'm not so sure about information and credentials of the MQTT server

Code:

const char* mqttServer = "???????????";
const int mqttPort = ??????;
const char* mqttUser = "?????????";
const char* mqttPassword = "???????????";

tnks