Common Protocols and Their Port Numbers
Service names and port numbers are utilized to differentiate between services used over transport protocols such as TCP/IP, UDP and SCTP. The organization responsible for assigning the name and port number of the services is called Internet Assigned Numbers Authority or IANA for short who also maintains the registries where service names and port numbers are stored.
Port registries used in transport protocols are divided into three ranges:
1-System Ports (0-1023)
2-User Ports (1024-49151)
3-Dynamic / Private Ports (49152-65535)
For service to operate efficiently, hosts that operate them and access them along with intermediate devices, like firewalls, must agree on which service is used on which port and many services will use the port listed on the IANA registry.
However, with the growing use of windows and single-user Linux systems over the years, the initial port model isn’t strictly adhered to, which means It may no longer be presumed that a particular port number automatically refers to a specific service. For example, web hosts launch multiple instances of the same service, so we cannot use the same port for all.
Nowadays there are hundreds and hundreds of programs and application-level protocols that have been delegated service names and port numbers along with this amount is set to increase later on. Additional confusion above port numbers may appear since IANA may de-assign a few more in usage and reassign it to a different service.
Here’s a table of the most common services and their port numbers
|
Service name |
Port number |
|
FTP |
20,21 |
|
SSH |
22 |
|
TELNET |
23 |
|
SMTP |
25 |
|
DNS |
53 |
|
DHCP |
67,68 |
|
HTTP |
80 |
|
HTTPS |
443 |
|
POP3 |
110 |
|
IMAP4 |
143 |
On Linux machines, you can find information about the services that client applications might use in the /etc/services folder.
On windows, services, port number and protocols are in the C:windows\system32\drivers\etc\services
Conclusion
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