It disables the use of authtype authentication, and can be used to temporarily disable a specific authentication type without having to re- compile telnetd . When terminal echo is not desired, a WILL ECHO is sent to indicate that telnetd will take care of echoing any data that needs to be echoed to the terminal, and then nothing is echoed. If a WILL ECHO is received, a DONT ECHO will be sent in response. DO SGA Indicates that it does not need to receive IAC GA, the go ahead command. Only sent if telnetd is compiled with support for linemode, and requests that the client do line by line processing.
Binary mode has no common interpretation except between similar operating systems.
The terminal type name received from the remote client is converted to lower case.