As a server administrator, it’s essential to understand the functions of common services and their respective port numbers. Similar to how an IP address determines the computer’s identity, the network port is key in identifying the specific application or service operating on that computer.
Without any doubt, I’m sure you’ve heard the term “port” before, but what does it mean in the world of computers?
What’s a Network Port?
In computer networking, a port is a virtual communication endpoint for exchanging data, which is pivotal in managing and directing internet traffic. In other words, you can imagine a network port as a virtual door on your computer.
However, unlike a physical port (like a USB one, for example), a network port is a software-based identification number that helps computers differentiate between multiple types of network traffic.
Typically, ports are identified by a specific network service assigned to them. Within an operating system, they serve as endpoints in the network communications process, primarily transferring data between a computer network and an application.
Understanding Network Port Ranges
Port ranges are a series of numbers assigned to various tasks and services in computer networking. These numbers range from 0 to 65535 and are divided into three different sub-ranges based on their use and the type of service they provide.
Understanding these ranges is key to effectively managing network security, traffic, and services.
| Range | Purpose | |
|---|---|---|
| Well-Known Ports | 0-1023 | Assigned to specific service by IANA (Internet Assigned Numbers Authority). These ports are reserved for common, widely-used services. For example, HTTP (web traffic) uses port 80, and HTTPS (secure web traffic) uses port 443. |
| Registered Ports | 1024-49151 | Ports that an organization can register with IANA to be used for a particular service. Many software manufacturers use these ports for their applications. |
| Dynamic or Private Ports | 49152-65535 | These are often used for client-side communication or temporary purposes. They are less regulated and more flexible in their usage. |
After discussing port rangers, let’s now briefly examine another fundamental aspect of networking: transport protocols.
Transport Protocols: The Digital Highways
Imagine the internet as a vast network of roads. Just like roads have traffic rules, the internet has transport protocols. These protocols are sets of instructions that manage how data packets move across the network.
TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are the most common protocols.
TCP: The Reliable Courier
TCP is a is a connection-oriented protocol. For example, when you send an email or load a webpage, TCP ensures that all the data packets reach their destination correctly.
If we were to make a comparison, we would say that TCP is like a reliable courier service. Letโs say you send a fragile package with tracking and insurance. TCP notices and sends a replacement if a packet gets lost or damaged.
This is why TCP is used for tasks where accuracy is crucial and is the most widely used networking protocol.
UDP: The Speedy Messenger
On the other hand, UDP is a connectionless protocol. This is due to the lack of overhead associated with creating, maintaining, and terminating connections.
So, itโs like a speedy messenger. UDP is used for tasks like live video streaming or online gaming, where receiving data quickly is more important than correctly receiving every packet.
With UDP, there’s no time spent checking if all packets have arrived or re-sending lost ones. Itโs all about speed, even if it means occasionally missing a piece of data.
Common TCP and UDP Default Ports
Now that we have introduced you to the fundamentals of a network port, its ranges, and the basic transport protocols, letโs move on to the main topic โ exploring the most common network ports out there.
As we delve into the specifics of each one, from well-known HTTP (port 80) and HTTPS (port 443) to others less familiar, we will uncover their roles in our daily digital interactions.
21 (TCP, UDP) – FTP
Port 21 is commonly associated with FTP (File Transfer Protocol). FTP is for transferring files between a client and a server. It’s usually regarded as a “non-secure” file transfer protocol.
FTP sends data in clear text and provides an anonymous option that does not require a password. However, FTP is a trusted and widely used protocol for transferring files.
22 (TCP, UDP) – SSH
SSH, or Secure Shell Protocol, is a network communication protocol used to perform operations on remote computers, but it may also be used for transferring data. A connection between the client and server is established whenever we run a command through the default SSH port number 22.
SSH was developed as a safe substitute for the unencrypted Telnet protocol, and it utilizes cryptographic techniques to ensure that all communication to and from the remote server is encrypted.
23 (TCP) – Telnet
The telnet protocol typically uses port 23. It’s often used for an administrative command-line interface in networking equipment such as routers and switches.
However, because the protocol is unencrypted, it’s usually only used safely within a local area network, as the data is in cleartext.
25 (TCP) – SMTP
Port 25 is the original standard email SMTP (Simple Mail Transfer Protocol) port and the oldest since it first debuted in 1982. After four decades, SMTP on port 25 is the basic standard for sending email between mail servers via the internet.
53 (TCP, UDP) – DNS
DNS (Domain Name System) turns domain names into IP addresses. As a result, thanks to DNS servers, people may type ordinary words into their browsers without remembering the IP address for each website.
DNS has been designed to use UDP and TCP port 53, with UDP being the default, and falls back to using TCP when it cannot communicate on UDP.
67,68 (UDP) – DHCP
DHCP (Dynamic Host Configuration Protocol) provides network addresses to dynamically configured TCP/IP network hosts. It uses UDP ports 67 and 68. The server should use port 67, and the client should use port 68.
80 (TCP) – HTTP
Port 80 is the port number assigned to the commonly used internet communication protocol HTTP (Hypertext Transfer Protocol). The HTTP protocol defines the format for communication between internet browsers and websites.
In other words, port 80 sends and receives web server requests. The web traffic that passes through the port remains in plain text.
110 (TCP) – POP3
POP3 (Post Office Protocol version 3) is a mail protocol to retrieve mail from a remote server to a local email client. It’s a relatively simple mail protocol, making it less prone to errors and more straightforward implementation. The default POP3 port is 110.
111 (TCP, UDP) – Portmapper
Portmapper service is required to run NFS both on the client and the server side. It runs on port 111 for both TCP and UDP protocols. Portmap makes the dynamic binding of remote programs possible.
137 (TCP, UDP) – NetBIOS
Port 137 is utilized by NetBIOS (Network Basic Input/Output System) Name service. NetBIOS’s primary purpose is to allow applications on different computers to communicate and establish sessions to access shared resources like files and printers and locate each other via a local area network (LAN).
143 (TCP, UDP) – IMAP
IMAP (Internet Message Access Protocol) is a mail protocol to access email on a local client’s remote web server. The IMAP protocol works on port 143, the default IMAP non-encrypted port.
161, 162 (UDP) – SNMP
The SNMP (Simple Network Administration Protocol) protocol suite collects network management and monitoring protocols. It’s often used to monitor firewalls, routers, switches, servers, printers, bridges, NAS disks, UPS, and other network devices.
SNMP ports are utilized via UDP on port 161 for SNMP Managers communicating with SNMP Agents and via UDP on port 162 when agents send unsolicited SNMP traps to the SNMP Manager.
443 (TCP) – HTTPS
HTTPS stands for HyperText Transfer Protocol Secure. Port 443, a web browsing port, is primarily used for HTTPS services. It’s a port that billions of people across the globe use every single day. Over 95% of secured websites use HTTPS via port 443 for secure data transfer.
587 (TCP) – SMTP
Port 587 is the standard secure SMTP (Simple Mail Transfer Protocol) port. It’s the default mail submission port. This is the one that will provide the best results when users submit an email to be routed via a proper mail server.
The use of port 587 in conjunction with TLS encryption ensures that email is sent securely and following the IETF’s requirements.
993 (TCP) – IMAPS
IMAPS (IMAP over SSL) means IMAP traffic travels over a secure socket to a secure port. When using an encrypted IMAP connection, the default port is 993. It helps ensure your safety and privacy on the internet.
Conclusion
In this article, we have journeyed through the most commonly used network ports, uncovering their pivotal roles in our everyday internet activities.
Understanding these is not just for IT professionals – it’s valuable knowledge for anyone who uses the internet, offering insights into how our online interactions are facilitated and secured.
See RFC 1700 or IANA for a complete list of network port numbers for more information.
