I thought it would be helpful to me to have the common network ports handy. I am Network+ certified, but sometimes I forget them.
|20 and 21||FTP||File Transfer Protocol is used for sending files to and from a server|
|22||SSH||The Secure Shell Protocol is used for sending encrypted data to a server|
|23||Telnet||Telnet is used for an providing an unsecure interface to a server shell|
|25||SMTP||The SMTP Protocol used for sending email between servers|
|53||DNS||The Domain Naming Service is used to match computer names to IP Addresses on a network|
|67||DHCP||The Dynamic Host Configuration Protocol enables client computers to obtain a valid IP address on a network|
|80||HTTP||HTTP allows clients to request web pages from servers|
|109, 110||POP||Allows clients to communicate with email servers to read messages in their mailbox|
|137-139||SMB||Microsoft servers use this for file and print sharing|
|143, 220||IMAP||Provides advanced mailbox services for clients|
|389||LDAP||LDAP provides access to directory services for authenticating|
|443||HTTPS||Provides encrypted communication with web servers|
|2049||NFS||Provides file sharing between Unix and Linux systems|
In my learnning environment, when I typed in cat /etc/services in bash it listed all of the services available on my linux server.