I don't write a TCP stack, but Juho Snellman writes a TCP stack for living, and I found the following anecdote on writing an interoperable TCP stack interesting

I don't write a TCP stack, but Juho Snellman writes a TCP stack for living, and I found the following anecdote on writing an interoperable TCP stack interesting. http://snellman.net/blog/archive/2014-11-11-tcp-is-harder-than-it-looks.html http://snellman.net/blog/archive/2014-11-11-tcp-is-harder-th... TLDR: There are TCP implementations that can't handle SYN retransmission which you have to interoperate if your TCP stack is the product.