In the mid 90's, I was very surprised to discover that a popular telnet program widely distributed in Linux distros was written in C++, with cruft like abstract base classes with pure virtual functions and whatnot.

(I was looking at the source because the stupid thing would disconnect whenever the PPP connection went donw; it was over-reacting to EHOSTUNREACH errors on the socket, which are recoverable; I fixed that, at least for myself.)

Here it is: https://github.com/marado/netkit-telnet/tree/master/netkit-t...