Telnetd returns echo back in "Don't ECHO"

Issue

• Telnetd returns echo back in spite of client program sending "Don't Echo". However telnetd always returns echo back in this situation. It seems to be changing from a client by the timing to which "Don't Echo" was sent. We hopes that echo back isn't always done.

• Could you confirm whether behavior of telnetd is assumed one or a problem? And, please tell me the way which doesn't always do echo back.

• Cases without echo back *1

client                      server
        <-- Do Echo    ---
        --- Won't Echo -->
        <-- Will Echo  ---
        --- Don't Echo -->
        <-- "login"    ---

• Cases with echo back *2

client                      server
        <-- Do Echo    ---
        --- Won't Echo -->
        <-- Will Echo  ---
        <-- "login"    ---
        --- Don't Echo -->