Telnet :

Purpose: Used to establish a remote connection to a server or network device for management and troubleshooting.

Protocol: Operates over the TCP/IP protocol.

Functionality: Allows users to execute commands on a remote machine as if they were physically present at the terminal.

Port: Typically uses port 23.

Use Case: Useful for network administrators to access and manage devices remotely, such as routers and switches.

Security: Not secure, as it transmits data, including passwords, in plain text. It is often replaced by more secure protocols like SSH.

Ping :

Purpose: Used to test the reachability of a host on an IP network and measure the round-trip time for messages sent from the source to the destination.

Protocol: Operates over the ICMP (Internet Control Message Protocol).

Functionality: Sends ICMP Echo Request packets to the target host and waits for Echo Reply packets.

Port: Does not use a specific port.

Use Case: Commonly used to check network connectivity, diagnose network issues, and measure network latency.

Security: Generally considered safe, but can be used in network attacks (e.g., Ping of Death)