Programs are free to use any port(s) they like, but there are many services that usually use a particular port number. The most common of these are listed here ...
7
Echo
Echo servers relay all data received back to their source
17
Quote Of The Day
Random quote of the day
19
Character Generator
'CharGen' servers transmit streams of data as soon as a client connects
20 File Transfer Protocol (FTP) - file
transfer
This port is used by FTP
to transfer files
21 File Transfer Protocol (FTP) - control
This port is used by FTP
to allow the client and server to communicate
23
Telnet
Telnet is a simple
console-style communications protocol
25
Simple Mail Transfer Protocol (SMTP)
SMTP is the most popular
mail transfer protocol on the Internet
43
Whois
Whois servers
contain information about IP and DNS addresses
53
Domain Name Server (DNS)
DNS translates IP
addresses to more human-readable addresses
80
Hypertext Transfer Protocol (HTTP) web server
HTTP is the
protocol used to transfer data on the World Wide Web (WWW)
109
Post Office Protocol (POP)
POP servers allow
you to check your email
110
Post Office Protocol (POP3)
The most popular
version of POP
113
Ident
Identification protocol,
returns info such as system type and username.
119
Network News Transfer Protocol (NNTP)
The protocol used
by newsgroups
135
Remote Procedure Call (RPC)
Usually the RPC Locator Service, a registrar for all other RPC services
137
NETBIOS Name Service
Used for local area
network address resolution
138
NETBIOS Datagram Service
Used for local area
network UDP transfers
139
NETBIOS Session Service
Used for local area
network TCP transfers
443
Hypertext Transfer Protocol Secure (HTTPS)
Securely encrypted
HTTP web transfer
1080 SOCKS
Proxy
A common proxy
server
1433
Microsoft SQL Server
Microsoft Structured Query
Language server
6667
Internet Relay Chat (IRC)
Internet Relay Chat
is a popular text-based chat medium
8080 Proxy
Commonly used as a
proxy for web servers
Red
- This port/service is usually only found on Unix/Linux systems.
Blue - This port/service is usually only
found on Microsoft Windows systems.
Black - This port/service can be found on multiple operating systems.
Other port numbers
To find out what services use any port number (and vice versa), simply use the Port Explorer Lookup utility.
Other notes
There are 65,535 TCP ports and 65,535 UDP
ports.
Most servers allow the admin to choose which port the server will listen on, so
for example if you find a server with port 80 open, it doesn't necessarily mean
there is a web server at that port..
ICMP doesn't use ports, it works at the same level as Internet Protocol (IP), as
seen in this diagram:
