Some telnet clients and servers agree to encrypt their communications, to prevent eavesdropping on the connection. Unfortunately, the hack used above (using the network connection that the telnet client has set up while the telnet client is idle) won't work in that case. Instead, one really must go through the telnet client itself, so it can do its encryption. It seems like that requires a simple hack to the telnet client itself, to add a command that runs a process with its stdin and stdout are connected to the live telnet connection. This would also be useful for various bots, so perhaps someone has already hacked it up.