2.1 - CompTIA A+ Core 1

TCP port 20

Used by File Transfer Protocol (FTP) for data transfers.

TCP port 21

Used by FTP for controlling data transfers.

Function of FTP

Transfers files between systems and includes file management functionalities.

TCP port 22

Used by Secure Shell (SSH) for encrypted communications.

Function of SSH

Allows encrypted communications between a client and a remote device's console/CLI.

TCP port 23

Used by Telnet for non-encrypted communications.

Function of Telnet

Allows non-encrypted communications between a client console/CLI and a remote device.

TCP port 25

Used by Simple Mail Transfer Protocol (SMTP) for sending emails.

Function of SMTP

Used to send client mail to a mail server and facilitate server-to-server mail communications.

UDP port 53

Used by Domain Name System (DNS) to resolve domain names to IP addresses.

Function of DNS

Resolves domain names to IP addresses, making it easier to access websites.

UDP ports 67/68

Used by Dynamic Host Configuration Protocol (DHCP) for automatically assigning IP addresses.

Function of DHCP

Automatically assigns IP addresses to network devices from a real-time IP pool.

TCP port 80

Used by Hypertext Transfer Protocol (HTTP) for client-webserver communications.

TCP port 443

Used by Hypertext Transfer Protocol Secure (HTTPS) for encrypted client-webserver communications.

TCP port 110

Used by Post Office Protocol 3 (POP3) for server to client mail transfer.

UDP port 137

Used by Network Basic Input/Output System (NetBIOS) for name services.

TCP port 139

Used for NetBIOS session services.

Function of IMAP

Used for multi-client email retrieval, allowing better management of emails.

UDP ports 161/162

Used by Simple Network Management Protocol (SNMP) for querying and receiving network traps.

TCP port 389

Used by Lightweight Directory Access Protocol (LDAP) for querying network directories.

TCP port 445

Used for Server Message Block (SMB) or Common Internet File System (CIFS) for file/printer sharing.

TCP port 3389

Used by Remote Desktop Protocol (RDP) for remote computer sharing.

Connectionless Protocols

Protocols like DHCP and Trivial File Transfer Protocol (TFTP) that do not establish a connection before data transfer.

Connection-oriented Protocols

Protocols like HTTPS and SSH that establish a connection before data transfer.