Common Ports and Error Codes in Networking

Common Port Numbers

• 20, 21: FTP (File Transfer Protocol)
• 22: SSH (Secure Shell)
• 23: Telnet (Unsecure Remote Login)
• 25: SMTP (Simple Mail Transfer Protocol)
• 53: DNS (Domain Name System)
• 67, 68: DHCP (Dynamic Host Configuration Protocol)
• 80: HTTP (HyperText Transfer Protocol)
• 110: POP3 (Post Office Protocol v3)
• 123: NTP (Network Time Protocol)
• 143: IMAP (Internet Message Access Protocol)
• 161, 162: SNMP (Simple Network Management Protocol)
• 443: HTTPS (HTTP Secure)

Common HTTP Error Codes

• 200 OK: The request was successful, and the server returned the requested data.
• 301 Moved Permanently: The resource has been permanently moved to a new URL.
• 400 Bad Request: The server could not understand the request due to malformed syntax.
• 401 Unauthorized: Authentication is required, and the user is not authorized.
• 403 Forbidden: The server understands the request, but the client does not have permission to access the resource.
• 404 Not Found: The server cannot find the requested resource.
• 408 Request Timeout: The server timed out waiting for the request.
• 500 Internal Server Error: A generic error occurred on the server.
• 502 Bad Gateway: The server received an invalid response from an upstream server.
• 503 Service Unavailable: The server is temporarily unavailable, usually due to maintenance or overload.