A modern normal network card will have onboard an Ethernet controller which, of course, is a pre-programmed microcontroller. Not only does it do the things required to keep a computer on the network, ...
A top-down exploration of networking using the 5-layer model and the TCP/IP stack. HTTP, FTP, DNS, BSD Sockets, concurrent servers, checksums, reliable transport with stop-and-wait, go-back-n, ...