Networking Ports Flashcards
And What They Do
PORT 21
FTP
File Transfer Protocol
FTP is the most common way of sending and receiving files between two computers. An example of how FTP is used today is by web developers, who connect to their web server using an FTP client or FTP program (e.g., FileZilla) to send (upload) updated versions of a web page.
PORT 22
SSH
Secure Shell
SSH (developed by SSH Communications Security Ltd.) is a secure protocol for remote logins. Using an SSH client, a user can connect to a server to transfer information in a more secure manner than other methods, such as telnet.
PORT 23
TELNET
A terminal emulation that enables a user to connect to a remote hostor device using a telnet client, usually over port 23. For example, typing telnet hostname would connect a user to a hostnamenamed hostname. Telnet enables a user to manage an account or device remotely. For example, a user may telnet into a computer that hosts their website to manage his or her files remotely. In the image to the right, is an example of a telnet session. As can be seen from this example, a telnet session is a command line interface.
PORT 25
SMTP
Simple Mail Transfer Protocol
SMTP is an Internet standard for the sending of e-mail messages over port 25. While it is mostly used for transfer from one mail server to another, some client mail applications use SMTP for relaying messages; whereas receiving happens via POP or IMAP.
PORT 53
DNS
Domain Name System
DNS is a service that receives a request containing a domain name hostname and responds with the corresponding IP address. The first DNS was designed and implemented by Paul Mockapetris and Jon Postel in 1983.
PORT 80
HTTP
Hypertext Transfer Protocol
HTTP is a set of standards that allow users of the World Wide Web to exchange information found on web pages.
Today’s browsers no longer require HTTP in front of the URL since it is the default method of communication. However, it is kept in browsers because of the need to separate protocolssuch as FTP.
PORT 110
POP3
Post Office Protocol
POP or POP mail is one of the most commonly used protocols used to receive e-mail on many e-mail clients. There are two different versions of POP: POP2 and POP3.
POP2 was an early standard of POP that was only capable of receiving e-mail and required SMTP to send e-mail.
POP3 is the latest standard and can send and receive e-mail only using POP, but can also be used to receive e-mail and then use SMTP to send e-mail.
PORT 143
IMAP
Internet Message Access Protocol
IMAP was first developed by Mark Crispin while at Stanford University in 1986. It is a protocol for retrieving e-mail from a server, similar to POP. The secure version of IMAP is called IMAPS, which stands for IMAP over SSL.
PORT 443
HTTPS
Hypertext Transfer Protocol Secure
HTTPS is a protocol which uses HTTP on a connection encrypted by transport-layer security. HTTPS is used to protect transmitted data from eavesdropping. It is the default protocol for conducting financial transactions on the web, and can protect a website’s users from censorship by a government or an ISP.
PORT 3389
RDP
Remote Desktop Protocol
RDP is the protocol that enables Remote Desktop Connection to communicate with Microsoft Terminal Services. The Remote Desktop Protocol is commonly accessed through port 3389.
PORTS 137 to 139
NetBIOS/NetBT
Network Basic Input/Output System
NetBIOS was developed by IBM, Microsoft, and Sytek. NetBIOS allows computers and applications to communicate with network hardware, and allow data to be transmitted properly over a network. For example, Microsoft Windows computers that are named in a workgroup and not a domain use NetBIOS names, which are converted to IP addresses.
NetBIOS commonly communicates on ports 137, 138, and 139. If your firewall blocks any of these ports you may get errors when your computer communicates with another computer that utilizes NetBIOS (e.g., MicrosoftWindows). To prevent these errors or warnings, you must provide access on these ports.
PORT 445
SMB
Server Message Block
SMB is a common network communications method used on Microsoft operating systems allowing those computers to communicate with other SMB computers.
CIFS
Common Internet File System
CIFS is a network file service protocol developed by Microsoft. It is used in conjunction with TCP/IP to facilitate file sharing across multiple platforms for a large number of simultaneous users.
PORT 427
SLP
Service Location Protocol
(SLP, srvloc) is a service discovery protocol that allows computers and other devices to find services in a local area network without prior configuration. SLP has been designed to scale from small, unmanaged networks to large enterprise networks. It has been defined in RFC 2608 and RFC 3224 as standards track document.
PORT 548
AFP
The Apple Filing Protocol
(AFP), formerly AppleTalk Filing Protocol, is a proprietary network protocol, and part of the Apple File Service (AFS), that offers file services for macOS and the classic Mac OS. In macOS, AFP is one of several file services supported, with others including Server Message Block (SMB), Network File System (NFS), File Transfer Protocol (FTP), and WebDAV.
PORTS 67/68
DHCP
Dynamic Host Configuration Protocol
DHCP is a protocol used to assign an IP address to a computer or device connected to a network automatically. Routers, switches, or servers that use DHCP to assign addresses to other computerscan make setup and management easier for the network administrator.
On a home network, DHCP can be set up by purchasing a home router, wireless router, or switch with NAT/DHCP and connecting each computer to it. If the network has a firewall, ports 67 and 68 need to be open for devices to function properly.
