A port number uniquely identifies a network-based application on a computer.A port number is the logical address of each application or process that uses a network or the Internet to communicate. In a server, more than one user process can use TCP at the same time. To identify the data associated with each process, port numbers are used. Port numbers are 16-bit, and numbers up to 65535 are possible.
We can say that A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server.
The port number is passed logically between client and server transport layers and physically between the transport layer and the Internet Protocol layer and forwarded on. Port numbers allow different applications on the same computer to share network resources simultaneously. When a client process first contacts a server process, it might use a well-known port number to initiate communication.
Authority for Port Number
The Internet Assigned Numbers Authority (IANA) is responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources. This includes the registration of commonly used port numbers for well-known Internet services. The port numbers are divided into three ranges: the well-known ports, the registered ports, and the dynamic or private ports. The well-known ports (also known as system ports) are those from 0 through 1023.
Here are some Important port number for you :
- 20: File Transfer Protocol (FTP) Data Transfer
- 21: File Transfer Protocol (FTP) Command Control
- 22: Secure Shell (SSH) Secure Login
- 23: Telnet remote login service, unencrypted text messages
- 25: Simple Mail Transfer Protocol (SMTP) E-mail routing
- 53: Domain Name System (DNS) service
- 67and 68: Dynamic Host Configuration Protocol (DHCP) servers use UDP port 67 to listen for requests while DHCP clients communicate on UDP port 68.
- 69: TFTP(Trivial File Transfer Protocol) TFTP offers a method of file transfer without the session establishment requirements that FTP uses. Because TFTP uses UDP instead of TCP
- 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web
- 88: The Xbox Live Internet gaming service uses several different port numbers including UDP port 88.
- 110: Post Office Protocol (POP3)
- 119: Network News Transfer Protocol (NNTP)
- 123: Network Time Protocol (NTP)
- 137/138/139 NetBIOS
- 143: Internet Message Access Protocol (IMAP) Management of digital mail
- 161and 162: Simple Network Management Protocol (SNMP)
- 194: Internet Relay Chat (IRC)
- 389 Lightweight Directory Access Protocol (LDAP)
- 443: HTTP Secure (HTTPS) HTTP over TLS/SSL
The registered ports are those from 1024 through 49151. IANA maintains the official list of well-known and registered ranges. The dynamic or private ports are those from 49152 through 65535. One common use for this range is for ephemeral ports.
Read also about Snapdragon Processor. Click Here