Port is an application-specific or process-specific software construct serving as a communications endpoint in a computer’s host operating system. Transport Layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP), specify a source and destination port number in their packet headers. A port number is a 16-bit unsigned integer, thus ranging from 1 to 65535. Port numbers are assigned based on three ways.

  • System ports  (ranging from  0- 1023)
  • User ports    (ranging from 1024-49151)
  • Dynamic/private ports   (ranging from 49152-65535)

There ports numbers as well as Internet Protocol Address are manage by Internet Assigned Numbers Authority (IANA).

Some commonly used port numbers are:-

HTTP 80 VMserver 902
HTTPS 443 RIP 510
DNS 53 Kerberos 464
DHCP 67,68 X11 6000-6001
Telnet 23 Postgres 5432
SSH 22 MS SQL 1433-1434
IMAP 143 cPanel 2082-2083
IMAP(SSL) 993 RADIUS 1812-1813
LDAP 389 Oracle DB 2483-2484
POP3 110 HTTP Proxy 3128
POP3 (SSL) 995 Appletalk 201
RPC 135 msql 4333
SMTP 25 mysql 3306
FTP 20,21 Terminal Server 3389
L2TP 1701 NFS 2049
Name Server 42 syslog 514
Echo 7 rlogin 513
MS exchange 102 VNS Server 5900+
WINS 1512 Open VPN 1194
NTP 123 NetBios 137-139
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