comptia a+ port numbers

CompTIA A+ Port Numbers: Important Things to Know in 2023

CompTIA A+ Port Numbers is an area that all Network+ test-takers should know. What should you know about this A+ exam part? Discover this in the below article.

April 25, 2022

CompTIA A+ Port Numbers part of the A+ certification exam is often considered one of the most challenging parts for most candidates. So what should you know about the CompTIA A+ ports and protocols part? In this article, we will provide you with the most up-to-date and beneficial information regarding this exam part. Let’s go ahead!

Don’t forget to take our free CompTIA A+ practice test to pass your exam on the first try with a high score.

What is a Communication Protocol?

2 or more people in a messaging system may communicate using any modification in a single measurement as long as the communication protocol is followed. A detection and correction procedure is defined in the protocol and may be used in the event that a communication breakdown occurs. Hardware, software, or a mix of the two can also be used to implement protocols.

Implementations may communicate with other computers through preset ports on a network adapter, thanks to protocols. A computer’s port number is used to identify protocols for the purpose of categorizing and organizing distinct procedures. Open a browser and enter in the address bar to access the site. The web server is connected using the Hypertext Transfer Protocol (HTTP). The web server uses an unused outgoing port on your computer to send and receive signals. Port 80 (the Link incoming port) on the central server is always accessible to enable computers to connect to the web server.

Transmission Control Protocol 

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The internet protocol suite’s TCP Transmission Control Protocol is a key component. TCP/IP started as a companion protocol to the Internet Protocol (IP) in the first network implementation. Applications operating on hosts interacting over an IP network may rely on TCP to transmit their data in a timely and error-checked manner. Because TCP is a connection-oriented protocol, data can only be transferred after a connection has been established between a client and a server. It is the responsibility of the transmitting computer to retransmit packets that are not received by the receiving computer since the receiving computer cannot put the message together without them.

An example of this is the case when the tires are not visible in an image sent by a computer, in which case TCP instructs that computer to retransmit those portions of the image so that it can be properly assembled.

User Datagram Protocol

Internet Protocol (IP) suite components include UDP (which is also known as User Datagram Protocol). Computer programs may deliver datagrams (messages) to other IP hosts using UDP. Communication channels and data pathways may be established without prior communication. The protocol methods in UDP are kept to a minimum since it relies on a connectionless communication paradigm.

To ensure the integrity of the data, UDP offers checksums and ports for the source and destination of the datagram. Unlike TCP, there are no handshakes and hence no assurance of delivery, ordering, or protection against duplication. This means that the user’s software is exposed to the network’s unreliability. Other than DNS, which is only used for basic requests and answers, UDP is used in VoIP and streaming media sessions.

Examples of TCP Versus UDP

Prerecorded YouTube videos are a good illustration of TCP. This is a video that has already been published to YouTube and is residing on a YouTube server someplace. Pre Recorded videos “Hey, I’m interested in watching this pre-recorded movie,” says the client’s computer as it sends out a request over TCP (three-way handshake) to the YouTube server (known as SYN, synchronize).

A message from the YouTube server reads, “Hello, how are you? That video is mine if you’d want to see it. “Would you be interested in seeing it?” “Synchronize-acknowledgement” is the technical term for this. The client computer answers by stating, “Yes, please.” (Acknowledgement is known as ACK). The video is subsequently “sent” across via the YouTube server. The 3-way handshake would have to be restarted at each interruption in the transmission of that video from the YouTube server to the client computer (also known as buffering), so that you may see the whole video in its entirety.

The live streaming of a video on YouTube is an example of UDP. There is a live broadcast on a YouTube channel of a YouTuber. You opt to watch the stream in real-time. Parts of a streaming video appear and disappear for a few seconds before returning to “normal” and picking up where they live broadcaster is now located in real-time. To verify that you (the client computer) have received the whole movie, the live stream does not engage in a three-way handshake via UDP. UDP live streams continue to send out data packets without checking to see whether the packets have been received by the viewer.

Unlike a live stream UDP transmission, where you could miss a few seconds here and there, TCP makes it a point to ensure that you get all of the packets sent to you. A live broadcast would need TCP to rebuild a three-way handshake every time the stream went in or out, and at whatever point in time that happened. In order to continue the live broadcast, you would have to wait for YouTube to relay the missing information before you could do so. As a result, you would be a few seconds or minutes behind the real YouTuber on the live broadcast.

Protocols were used for different purposes in the instances above. Even though UDP is less dependable than TCP, it is the superior option for time-sensitive information. TCP may be useful in other circumstances, such as where security and dependability are top priorities. It’s important to remember that you’re connecting to a server via the incoming ports.

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File Transfer Protocol

Personal documents may be transferred between a client and a server on a network using the File Transfer Protocol (FTP). Web browsers also make use of FTP. The prefix ftp:/ is used to connect to an FTP server. Enter FTP, hit Enter, and then type help at the FTP prompt to view the arguments you might be using on Windows, Linux, and macOS.

Anonymous FTP is supported by FTP sites that allow anybody to download files. Archive sites use anonymous FTP to make their archives available to the broader public. These websites generate an “anonymous” user account. Admission to the archive host and other operational constraints are restricted to “anonymous.” A user account may be required to access some FTP sites. Because FTP default passwords are transferred and verified in clear text, it is regarded as less secure than other file transfer protocols. FTP with SSL/TLS (FTPS) or Secure File Transfer Protocol (SFTP) may be used to enhance security (SFTP). Port 21 is used by FTP.

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Secure Shell

An untrusted network may be protected by using the SSH Secure Shell encryption protocol called. FTP and Telnet are less secure options when compared to SSH. SSH may be used to secure any network service, including remote code execution access, login, and operation implementation. A consumer would also have to establish port 22 on the SSH server in order to extract useful information they are looking for. While conventional FTP uses an insecure port (TCP port 22), Secure FTP (SFTP) uses a secure port (TCP port 22) and an SSH transaction to operate over it.


Using a virtual terminal connection, Telnet would be a web or LAN-defined recruitment policy for simultaneous participatory text-based communication. It is possible to connect to an external host or device through port 23 with the help of a Telnet emulator. Users may access their platform’s host controller via telnet access, rather than downloading files and pages as they would with a http:// or ftp:/ connection. Until a distant computer is configured to allow a Telnet login on port 23 and that port is open, the connection from a user cannot be created.

A command-line Telnet application may be used to start a command prompt (Windows) or Terminal (Linux) on a remote computer, and then type telnet and hit the Enter key to access the Telnet command-line prompt. Type help and click Enter to get assistance with commands. SSH has supplanted Telnet as the preferred method of connecting to remote servers in current versions of macOS. However, if Telnet is still required, it may be set up.

Simplified Mail Transfer Protocol 

Simplified Mail Transfer Protocol (SMTP) is a method of transmitting emails. For sending and receiving emails, SMTP employs port 25 and the SMTP protocol. A client device should verify with the internet service provider or organization that offers internet access for email settings such as server type (SMTP, POP3, or IMAP), port(s) utilized, username/password for access to the server(s), and security options (whether SSH is used).

Domain Name System

Using DNS, computers, services, and other resources on the internet or a private network may be named in an organized and decentralized manner. Domain names are used to store a variety of data about the participants. IP addresses are used to locate and identify computer services and devices with the underlying network protocols based on domain names that are easier to remember.

If you think about it this way, DNS may be likened to a phone directory for your computer network. Simply typing into your user device’s google search bar will use the DNS to find and connect you to Google’s IP address, saving you from having to keep track of a long list of IP numbers only to go to a popular website like Google.

It is common practice to specify the DNS server’s IP address (or multiple DNS server IP addresses) when manually establishing an IP address. Port 53 is used by DNS. Even though DNS is technically incorrect, many IT professionals use the term “domain registration service” or “domain name server” interchangeably.

Hypertext Transfer Protocol

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Application protocols for distributed, collaborative hypermedia information systems use the HTTP/HTTPS Hypertext Transfer Protocol. Hypertext texts that incorporate hyperlinks to other resources may be quickly accessed by a mouse click or by touching the screen in a web browser, for example. HTTP is the backbone of data transfer for the World Wide Web.

Web browsers like Internet Explorer, Microsoft Edge, and Firefox & Chrome all employ HTTP as a standard communication protocol. The prefix http:// is used for unencrypted webpages, whereas the prefix https:// is used for encrypted sites (HTTP Secure or HTTPS). Ports 80 and 443 are used for HTTP and HTTPS respectively. If a website is secure, a closed padlock symbol will appear next to the website’s URL in the web address bar of most browsers.

Post Office Protocol version 3

Protocol version 3 is used by email clients to download messages from a mail server. On a local computer, incoming email is saved in a specific folder. Using POP3 email is not a good option for those who regularly move between desktops and/or mobile devices, since the email is only downloaded after a client device requests it. For the most part, those that use POP3 servers for their email retrieval use SMTP for their outgoing messages. Port 110 is used by POP3, the most recent version and standard.

Internet Message Access Protocol

In order to get email messages from a mail server via an IP connection, email clients employ the Internet standard protocol IMAP, or Internet Message Access Protocol. Because IMAP was built to allow for comprehensive administration of an email box by various email clients, clients tend to keep messages on the server so that they may be accessed from any place until the user actively deletes them. IMAP4 is the most recent iteration of the protocol. In order to set up an IMAP-based email account, you must choose IMAP as the email server type, give the server’s name, your username/password, and whether the server utilizes SSL. Port 143 is used by IMAP.

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Common Internet File System

It’s called the Common Internet File System (CIFS) because it’s a method of allowing computers on a network to share access to shared files, printers, and serial ports. Additionally, packets that authenticate distant systems are used for interprocess communication. When utilizing NetBT, SMB communicates across ports 137-139, but when using TCP, SMB communicates through port 445. Sharing files across business intranets and the internet was initially facilitated via CIFS. CIFS has been supplanted by newer SMB versions in many cases (SMB 2.0 and 3.0).

Using the SLP Service Location Protocol, PCs and other devices may discover services on a LAN without the need for any previous setup or setup of their own. As a result of SLP, devices may share their configuration data with hosts. A key feature of SLP is its ability to grow with any network, whether it is small or big, managed or unmanaged. SLP is used by devices on a local network, such as printers, to notify other devices of their existence. Before SLP, devices had to be set up for individual services. It connects to port 427.

Apple File Service

File services for macOS and the traditional Mac OS are provided via the Apple File Service (AFS), which includes the Apple Filing Protocol, a proprietary network protocol formerly known as AppleTalk Filing Protocol. For transmission, Apple Filing Protocol relies on TCP/IP and port 548. Apple’s Time Machine data backup software and macOS 10.9 (Mavericks) employ AFP for communication with devices running previous versions of macOS.

In order to connect to another computer across a network, a user may utilize Microsoft’s RDP Remote Desktop Protocol, a proprietary Microsoft protocol. Using RDP client software (Remote Desktop Services) and RDP server software, a user may access another computer’s desktop (Remote Desktop Connection).

Dynamic Host Configuration Protocol

It is a network management protocol for IP networks called DHCP Dynamic Host Configuration Protocol (DHCP DHP), and it allows a DHCP server to dynamically assign an IP address and other network configuration parameters to each device on the network so that they can communicate with other IP networks.

Allowing computers to automatically request IP addresses and networking characteristics from the Internet service provider (ISP) reduces the need for network administrators or users to manually assign IP addresses for all network devices. You must manually give an IP address to a computer or other device, or you must use an APIPA address, which does not allow it to interact beyond the local network in the absence of a DHCP server.

Your IP address may vary often if you obtain it from a DHCP server, which assigns your address dynamically. Static addresses, such as those provided by a network administrator to printers and servers, are required by certain network devices. Thus, the gadgets become more dependable and accessible in the long run. Ports 67 and 68 are utilized by DHCP, with port 67 serving as the server’s destination and port 68 serving as the client’s.

Simple Network Management Protocol

It is an internet standard protocol for collecting and organizing information about controlled devices on IP networks, as well as altering that information to alter the behavior of those devices. Cable modems, routers, switches, servers, workstation computers, and printers are just some of the devices that generally support SNMP and are frequently integrated into software known as a network management system (NMS).

Everything SNMP-based on a computer is controlled by the NMS, which is installed on the computer known as a manager. ‘Managed devices,’ as the term implies, refer to the monitored gadgets. In order to keep track of the managed devices, NMS deploys a little piece of software called an agent. Ports 161 and 162 are designated for SNMP traffic on a network.

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Lightweight Directory Access Protocol

A vendor-neutral, independent, and industry-standard application protocol for accessing and maintaining distributed directory information services over an IP network, LDAP (Lightweight Directory Access Protocol) was developed by the Open Group. When it comes to building intranet and internet applications, domain directory services are essential because they enable people, systems, networks, services, and applications to share information with each other across the network.

A corporate email directory is an example of a directory service that provides an ordered collection of data, generally with a hierarchical structure. Directory services are the Microsoft term for this. Port 389 is used by LDAP.

CompTIA A+ ports are difficult, but you can completely ace this part if you have enough studying time, effort, and preparation. We hope that this article about CompTIA A+ port numbers can do wonders for you during the process of taking and passing this IT exam.