The fact that Telnet is actually a protocol, and a weird one (mostly because it's ancient and actually predates UNIX). I believe the reason is that those keypre

The fact that Telnet is actually a protocol, and a weird one (mostly because it's ancient and actually predates UNIX). I believe the reason is that those keypresses are not interpreted by your terminal but instead sent over to the other side to be interpreted there. Obviously, they don't do anything there. With "nc towel.blinkenlights.nl 23", on the other hand, they would work.