Network Port Number

Network Port Number

Port Number is a 16-bits number. It is used as a address to identify the app/process on a machine. IP address identifies a host, the port number identifies the process on that host.

Port number is used by TCP and UDP.

Port numbers are divided into three ranges:

• well-known ports
• registered ports
• dynamic or private ports

Well-known ports are those from 0 through 1023. Examples:

• 20 and 21: FTP
• 22: SSH (for secure remote command line access.)
• 23: Telnet (for remote command line access)
• 25: SMTP (for sending email)
• 53: DNS
• 80: HTTP
• 110: POP3 (for receiving email)
• 143: IMAP. (for receiving email, improved POP)
• 161: Simple Network Management Protocol (SNMP)
• 443: HTTPS. (secure web, for example, online banking, shopping)

here's a complete list. List of TCP and UDP port numbers