An existing connection was forcibly closed by the remote host

i am using the sample CreateTicket class as below

https://github.com/freshdesk/fresh-samples/blob/master/C-Sharp/CreateTicket.cs

and it throws connection error on request.GetRequestStream(); 

"An existing connection was forcibly closed by the remote host"

has any one else notice this and is aware of any workaround.

We are using the API key not username and password and the end points are correct as well.