If you do forget the ports used by protocols or the function of internet protocols, don’t worry i have compiled a list of all the possible commonly used protocols along with the port used by them and a short definition of each one. If you think i have missed some kindly mention it in comments and i will update this post.
DHCP (Dynamic host configuration protocol) Port 67/68:
DHCP is a method of assigning and controlling the IP addresses of computers on a given network. It is a server based service that automatically assigns IP numbers when a computer boots. This way the IP address of a computer does not need to be assigned manually.
FTP (File Transfer Protocol) port 20/21:
Allows file transfer between two computers with login required.
TFTP (Trivial File Transfer Protocol ) port 69:
Allows file transfer between two computers with no login required.TFTP is typically used by devices to upgrade software and firmware; this includes Cisco and other network vendors’ equipment.
FTP over TLS/SSL port 989/990:
FTP over TLS/SSL uses the FTP protocol which is then secured using either SSL or TLS.
SMTP (Simple Mail Transfer Protocol) port 25:
POP 3 (Post Office Protocol) port 110:
POP protocol is used to retrieve mail from a server. POP was designed to be very simple by allowing a client to retrieve the complete contents of a server mailbox and then deleting the contents from the server.
DNS (Domain Name Service) port 53:
DNS translate domain names into IP addresses, typically for network routing.
HTTP (Hypertext Transfer Protocol) port 80:
HTTP is the main protocol that is used by web browsers and is thus used by any client that uses files located on these servers.
HTTPS (Hypertext Transfer Protocol over SSL/TLS ) port 443:
HTTPS is used to provide the same services as HTTP but doing it using a secure connection which is provided by either SSL or TLS.
NTP (Network Time Protocol) port 123:
NTP is one of the most used protocol. NTP is used to synchronize the devices on the Internet. Even most modern operating systems support NTP as a basis for keeping an accurate clock. The use of NTP is vital on networking systems as it provides an ability to easily interrelate troubles from one device to another as the clocks are precisely accurate.
IMAP (Internet Message Access Protocol) port 143:
IMAP version3 is the second of the main protocols used to retrieve mail from a server. While POP has wider support, IMAP supports a wider array of remote mailbox operations which can be helpful to users.
SNMP (Simple Network Management Protocol) port 161/162:
SNMP is used by network administrators as a method of network management. SNMP has a number of different abilities including the ability to monitor, configure and control network devices.
BGP (Border Gateway Protocol) port 179:
A dynamic router protocol to communicate between routers on different systems.
hope this will help somebody.