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

If Running In A .Net 4.5.2 Service

For me the issue was compounded because the call was running in a .Net 4.5.2 service. I followed @willmaz suggestion but got a new error.

In running the service with logging turned on, I viewed the handshaking with the target site would initiate ok (and send the bearer token) but on the following step to process the Post call, it would seem to drop the auth token and the site would reply with Unauthorized.

It turned out that the service pool credentials did not have rights to change TLS (?) and when I put in my local admin account into the pool, it all worked.