Where does the socket timeout of 21000 ms come from?

Question

The Problem

An app I\'m maintaining keeps getting socket timeouts after approximately 21000 ms, despite the fact that I\'ve explicitly set longer ti

Answer 1

It seems like it is a Windows default configuration...

https://social.technet.microsoft.com/Forums/windows/en-US/9e7f59dd-6469-4ade-91ca-ceb5bcaf2675/windows-7-tcp-parameter-tcpmaxconnectretransmissions-and-tcpinitialrtt?forum=w7itpronetworking

Based on the link and some further reading, Windows will by default do 3 retries and double the timeout with each attempt, starting a s 3sec one. So you end up with 3sec + 6sec + 12sec = 21sec timeout.