The confinement is a good period to refresh this software-only project and here is the new version !
3 years after the last version, I have cleaned up the TCP/IP code. IPv6 handling is removed because never used in practice, I added more checks and a few portability helpers that would help with MacOS and Win32. I also simplified several cases where strlen() can be replaced by sizeof() because the strings are constants.
I have a few more days to work on this and hopefully there will be more significant enhancements !
BTW, does this new version work on your computer(s) ?