Common TCP ports and TCP port ranges

TCP ports can use numerical values between 0 and 65,535.

Port numbers between 0 and 1023 are well known ports.

I will list a few commonly used ports:

20 and 21 are used for FTP. FTP stands for file transfer protocol.

22 is used by SSH or secure shell. It encrypts communications.

23 - is used by telnet. Telnet does not use encryption to transfer the data, so please consider using SSH instead.

25 is assigned to SMTP. SMTP stands for Simple Mail Transfer Protocol.

53 is assigned to DNS. DNS stands for Domain Name System.

67, 68 are being used by DHCP. DHCP stands for Dynamic Host Control Protocol. DHCP is responsible for dynamically assessing IP addresses. It is wise to use dynamic IPs for client machines, but not for the servers. Dynamic IPs may change, and this not you want to have for servers.

80 - is used for HTTP. HTTP uses unencrypted communication.

110 - is used by POP3, it is used to retrieve email.

137 and 139 are used by NetBIOS.

143 - IMAP. IMAP stands for Internet Mail Access Protocol.

161, 162 - are used by SNMP. SNMP stands for simple network management protocol.

389 - LDAP. LDAP stands Lightweight Data Access Protocol. 

443 - it is used by HTTPS. Letter ‘S’ at the end of this word stands for secure. HTTPS protocol needs to be used whenever private information is transmitted. For example these could be passwords of financial information. Encrypting data comes at higher processor utilization. Some companies decide to encrypt all of the network traffic.

445 - is used by SMB. SMB stands for Server Message Block, it is used by Windows computers to do file sharing.

3389 - RDP. Word RDP is the abbreviation of words Remote Desktop Protocol. RDP is used by Windows systems to perform remote management activities.



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