An existing connection was forcibly closed by the remote host

This generally means that the remote side closed the connection (usually by sending a TCP/IP RST packet). Possible causes include:

• You are sending malformed data to the application (which could include sending an HTTPS request to an HTTP server).
• The network link between the client and server is going down for some reason.
• You have triggered a bug in the third-party application that caused it to crash.
• The third-party application has exhausted system resources.

It's likely that the first case is what's happening.