A client-server protocol used to start a bidirectional/command line text interaction over a LAN or Internet is known as which protocol?

• A. Telnet
• B. SSH
• C. FTP
• D. SMTP

Answer: (A)

Telnet enables a bidirectional, text-based remote login session between a client and a server. It works by establishing a TCP connection and presenting a command-line interface on the server side, so whatever you type appears as input to a shell and the shell’s output is sent back to your screen in real time. This makes it ideal for starting an interactive, text-driven session over a LAN or the Internet. However, Telnet sends all data in plaintext, including credentials, which is why it’s considered insecure and is largely replaced by SSH for remote management. The other options don’t describe an interactive shell: FTP is for file transfers, and SMTP is for email handling. SSH is a secure alternative that provides the same interactive capability but with encryption.