Ports are the input/output points of devices on the network. Port numbers are one of the important issues that system administrators and security researchers should be aware of.
For example; A system administrator should know that when setting up a server with a website, they need to open port 80 in their system. He should also know that port 53 must be opened for name servers, i.e. DNS servers, that connect domains to IP addresses. These examples can multiply in this way.
There are 65535 port numbers in total. Ports 0 through 1024 are for the most commonly used applications. Port numbers 1024-49151 are reserved. The ports other than the reserved ones are dynamic ports and are open for private use. The following list lists the most commonly used port numbers.
1 TCP Port Service Multiplexer (TCPMUX)5 Remote Job Entry (RJE) 7 ECHO
18 Message Send Protocol (MSP)20 FTP — Data
21 FTP — Control
22 SSH Remote Login Protocol 23 Telnet
25 Simple Mail Transfer Protocol (SMTP)29 MSG ICP
37 Time
42 Host Name Server (Nameserv)43 WhoIs
49 Login Host Protocol (Login)53 Domain Name System (DNS)69 Trivial File Transfer Protocol
(TFTP)
70 Gopher Services
79 Finger
80 HTTP
103 X.400 Standard
108 SNA Gateway Access Server 109 POP2
110 POP3 115 Simple File Transfer Protocol (SFTP)118 SQL Services
119 Newsgroup (NNTP)123 Network Time Protocol (NTP)137 NetBIOS Name Service 139 NetBIOS Datagram Service 143
Interim Mail Access Protocol (IMAP)150 NetBIOS Session Service
156 SQL Server
161 SNMP
179 Border Gateway Protocol (BGP)190 Gateway Access Control Protocol (GACP)
194 Internet Relay Chat (IRC)197 Directory Location Service (DLS)389 Lightweight Directory Access Protocol (LDAP)396 Novell Netware over IP 443 HTTPS 444 Simple Network Paging Protocol (SNPP)
445 Microsoft-DS
458 Apple QuickTime
546 DHCP Client
547 DHCP Server
563 SNEWS
569 MSN
631 Internet Printing Protocol
1080 Socks