Can you give examples of response codes used in communication or protocols?

In communications and protocols, standard response codes are often used to indicate the result of a request. Here are some examples:

• HTTP codes:

  • 200 OK — request successfully completed.
  • 404 Not Found — resource not found.
  • 500 Internal Server Error — internal server error.

• FTP codes:

  • 220 — service ready for a new connection.
  • 331 — username accepted, password required.
  • 550 — requested file not available.

• SMTP codes:

  • 250 — command successfully executed.
  • 354 — server ready to receive data.
  • 550 — requested address not available.

These codes help the client and server understand the status of the operation and take appropriate actions.