An existing connection was forcibly closed by the remote host

Question

I am working with a commercial application which is throwing a SocketException with the message,

An existing connection was forcibly closed by the rem

Answer 1

Had the same bug. Actually worked in case the traffic was sent using some proxy (fiddler in my case). Updated .NET framework from 4.5.2 to >=4.6 and now everything works fine. The actual request was:
new WebClient().DownloadData("URL");
The exception was:

SocketException: An existing connection was forcibly closed by the remote host