TCP Retransmit and TCPCopy when using loopback device on Windows 7

Question

I have two programs running on the same Windows 7 System which connect via TCP. The server transmits unencoded VGA resolution images to the client in regular intervals.

The problem is, that from time to time, the transmission speed goes down by a factor of ~10 or so and stays that way for some time or until the client process is restarted.

I used the sysinternals process monitor to get some inside in what is going on. When the transmission speed is reduced I can see that following an initial TCP Send event on the server side, I eventually (after a couple of receive/send pairs) get a number of TCPCopy events on the client side followed by a ~300ms pause in which no TCP events are recorded, followed by a TCP Retransmit event on the server side. I only get those TCPCopy events and the retransmit event when the speed is reduced.

I tried to find out what the TCPCopy event is all about but did not find a lot on the internet.

I have two questions:

1. What is the TCPCopy event?

2. What does the TCPCopy event and the Retransmit event tell me about the problems in the TCP connection?

Answer 1

TCPCopy event represented by antivirus softwares sometimes. And many on i saw on web, people who deactivate their antivirus software that was fixed the issue. Especially Eset Nod32. Please try to deactivate your antivirus software both on server and client side and check it again.