Increase the TCP receive window for a specific socket

Question

How to increase the TCP receive window for a specific socket? - I know how to do so for all the sockets by setting the registry key TcpWindowSize, but how do do that for a specific one?

According to MSFT's documents, the way is

Calling the Windows Sockets function setsockopt, which sets the receive window on a per-socket basis.

But in setsockopt, it is mentioned about SO_RCVBUF :

Specifies the total per-socket buffer space reserved for receives. This is unrelated to SO_MAX_MSG_SIZE and does not necessarily correspond to the size of the TCP receive window.

So is it possible? How?

Thanks.

Answer 1

SO_MAX_MSG_SIZE is for UDP. Here's from MSDN:

SO_MAX_MSG_SIZE - Returns the maximum outbound message size for message-oriented sockets supported by the protocol. Has no meaning for stream-oriented sockets.

It's also not settable.

For TCP just use SO_(SND|RCV)BUF.

Answer 2

I am fairly sure that SO_RCVBUF is what you want. The first link says that SO_RCVBUF has the highest priority for determining the TCP window size over and above anything set on the system. From the way I am reading it, I think that all second part is saying is that the SO_RCVBUF size does not have to match the system receive window size. In other words, it can be a different size that you set.