IP Well Known Port Numbers/ Common TCP


COMMON TCP IP WELL KNOWN PORT NUMBERSOne key aspect of network and security engineer is to have a good understanding of well-known services and their port numbers (TCP and UDP).

Well Known Port Numbers Information

Below is a list of commonly used well-known protocols and their port number. Additionally, RFC reference will help to have more detail on the enlisted transport-layer common port numbers

Related- TCP vs UDP

20, 21TCPFile Transfer Protocol (FTP)RFC 959
22TCP and UDPSecure Shell (SSH)RFC 4250-4256
23TCPTelnetRFC 854
25TCPSimple Mail Transfer Protocol (SMTP)RFC 5321
53TCP and UDPDomain Name Server (DNS)RFC 1034-1035
67, 68UDPDynamic Host Configuration Protocol (DHCP)RFC 2131
69UDPTrivial File Transfer Protocol (TFTP)RFC 1350
80TCPHyperText Transfer Protocol (HTTP)RFC 2616
110TCPPost Office Protocol (POP3)RFC 1939
119TCPNetwork News Transport Protocol (NNTP)RFC 8977
123UDPNetwork Time Protocol (NTP)RFC 5905
135-139TCP and UDPNetBIOSRFC 1001-1002
143TCP and UDPInternet Message Access Protocol (IMAP4)RFC 3501
161, 162TCP and UDPSimple Network Management Protocol (SNMP)RFC 1901-1908, 3411-3418
179TCPBorder Gateway Protocol (BGP)RFC 4271
389TCP and UDPLightweight Directory Access ProtocolRFC 4510
443TCP and UDPHTTP with Secure Sockets Layer (SSL)RFC 2818
500UDPInternet Security Association and Key Management Protocol (ISAKMP) / Internet Key Exchange (IKE)RFC 2408 - 2409
636TCP and UDPLightweight Directory Access Protocol over TLS/SSL (LDAPSRFC 4513
989/990TCPFTP over TLS/SSLRFC 4217

Download the table here.

well known ports






Related- Difference between IP Address and Port Number

Related- Ports and Socket


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