Webhook subscription issue

I need to subscribe for telephony notification for that I am following
https://github.com/grokify/ringcentral-demos-webhooks
this is my request json
Request JSON:
{
"eventFilters": [
"/restapi/v1.0/account/~/extension/" ],
"deliveryMode":{
"transportType":"WebHook",
"address":"http://localhost:8080/hook";
}}
below is response

_json: {

errorCode: 'SUB-522',

message: 'WebHook responds with incorrect HTTP status. HTTP status is 404',

errors: [Array],

status: '404'

}

What wrong am I doing? Please guide me.

Thanks.