Common Port Numbers Every IT Professional Must Know

 Port number is a logical identifier used by computers to know which application or service should receive network data

Key Aspects of Port Numbers

  • Purpose: They ensure data, such as a website request, reaches the specific program (e.g., a web browser) instead of just the machine itself, acting like an apartment number in an address.
  • Range: Ports range from 0 to 65535, divided into Well-Known Ports (0-1023), Registered Ports (1024-49151), and Dynamic/Private Ports (49152-65535)
  • Protocols: Used by TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) to route information to the correct application. 

Note: Port number is different from IP Address

An IP address identifies a device on a network, while a port number identifies the specific process or application on that device. 


Why port numbers are needed ?

one computer can run many services at the same time:

  • Web server
  • email Server
  • Remote Access
  • File sharing
 Port numbers tell the operating system(OS) where to send the traffic

Example: 

    When you open any website: https://techstack-it.blogspot.com

      Browser connects to: techstack-it.blogspot.com:443

    • 443 = HTTPs Service


    Active Directory Port Numbers:

         AD Service               Port

      AD Web Services             9389

          DHCP Server             67

          DHCP Client             68

                  DNS             53

             Kerberos             88

                 LDAP             389

                LDAPs             636

                  SMB             445

                  RDP             3389

               TELNET             23

  RPC Endpoint Mapper             135

        Global CatLog             3268

  Global CatLog over SSL          3269

          RPC Dynamic             49152 - 65535



Most Important Well - Known Ports (0-1023)        

        Service         Port

         FTP              21

           SSH               22

         Telnet              23

           SMTP              25

            DNS              53

           HTTP              80

           POP2              109

           POP3              110

           NNTP              119

            NTP              123

           SNMP              161

           IMAP              143

          HTTPs              443

            SMB              445

           LDAP              389

          LDAPs              636



Common Registered Ports (1024-49151)

     Service            Port

         RDP                3389

          MySQL              3306 

      PostgreSQL             5432

       Oracle DB             1521

        Mango DB             27017

        Docker               2375/2376

    Kubernetes API           6443

        HTTP Proxy           8080



Dynamic/Private Ports (49152-65535)

  • Used temporarily
  • Assigned automatically
  • Commonly used for:
            1.  Client connections
            2. RPC
            3. High-traffic server apps


port Numbers Ranges:

  • (0 - 1023) is called Well-Known ports used by Core System Services.
  • (1024 - 49151) is called Registered ports used by Application and Servers.
  • (49152 - 65535) is called Dynamic/Private ports used by Temporary Clients.



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