Common Network Ports Reference: A Complete Guide

March 16, 2026 · 8 min read

What Are Network Ports?

Network ports are virtual communication endpoints that allow multiple services to run on a single device. If an IP address is like a building's street address, ports are the individual apartment numbers inside that building. When data travels across the internet, it's directed to a specific IP address and port number, ensuring it reaches the right application.

Every time you browse the web, send an email, transfer a file, or stream video, your device uses network ports to manage these different conversations simultaneously. Your web browser might be talking to port 443 on a web server while your email client communicates with port 993 on a mail server — all at the same time, on the same internet connection.

Port numbers range from 0 to 65,535. Each number can be associated with a specific service or application. Some port numbers are standardized and universally recognized (like port 80 for HTTP), while others are dynamically assigned as needed. Understanding common port numbers is fundamental knowledge for anyone working with networks, servers, or web applications.

TCP vs UDP

Before diving into specific port numbers, it's important to understand the two main transport protocols that use ports:

TCP (Transmission Control Protocol)

TCP is the reliable, connection-oriented protocol. It establishes a connection before sending data (the "three-way handshake"), ensures every packet arrives in the correct order, and retransmits any lost data. Think of TCP like a phone call — you establish a connection, have a conversation, and both sides know when the call ends.

TCP is used when data accuracy is critical: web browsing, email, file transfers, and database queries all use TCP because losing or reordering data would cause problems.

UDP (User Datagram Protocol)

UDP is the fast, connectionless protocol. It sends data without establishing a connection first and doesn't wait for confirmation of receipt. Think of UDP like sending postcards — you drop them in the mailbox and hope they arrive, but you don't wait for a response before sending the next one.

UDP is used when speed matters more than perfect reliability: video streaming, online gaming, VoIP calls, and DNS queries use UDP because a slightly dropped frame or delayed packet is better than pausing to retransmit.

Port Number Ranges

The 65,536 available ports are organized into three ranges:

• Well-Known Ports (0-1023): Reserved for standard system services and assigned by IANA (Internet Assigned Numbers Authority). These include the most commonly recognized ports like HTTP (80), HTTPS (443), and SSH (22). On Unix/Linux systems, binding to these ports typically requires root privileges.
• Registered Ports (1024-49151): Assigned to specific applications and services by IANA upon request. These include database servers (MySQL on 3306, PostgreSQL on 5432), application servers, and many commercial software products.
• Dynamic/Private Ports (49152-65535): Used temporarily by client applications for outgoing connections. When your browser connects to a website, it uses a random port from this range as the source port. These are also called ephemeral ports.

Essential Ports Every Admin Should Know

Here's a comprehensive reference of the most important network ports:

Web and Internet

• Port 80 (TCP) — HTTP: Standard web traffic. When you visit a website without specifying a port, this is the default. Still widely used, though increasingly replaced by HTTPS.
• Port 443 (TCP) — HTTPS: Encrypted web traffic using SSL/TLS. The standard for secure websites, online banking, shopping, and any site handling sensitive data. The most important port on the modern internet.
• Port 8080 (TCP) — HTTP Alternate: Commonly used for web proxies, development servers, and alternative web services. When port 80 is in use, 8080 is the conventional alternative.
• Port 8443 (TCP) — HTTPS Alternate: The secure counterpart to 8080, used for alternative HTTPS services.

Email

• Port 25 (TCP) — SMTP: Simple Mail Transfer Protocol for sending email between servers. Often blocked by ISPs to prevent spam.
• Port 465 (TCP) — SMTPS: SMTP over SSL for secure email submission.
• Port 587 (TCP) — SMTP Submission: The recommended port for email clients to submit outgoing mail with authentication.
• Port 110 (TCP) — POP3: Post Office Protocol for retrieving email. Downloads messages to the client.
• Port 995 (TCP) — POP3S: POP3 over SSL for secure email retrieval.
• Port 143 (TCP) — IMAP: Internet Message Access Protocol for accessing email. Syncs messages across devices.
• Port 993 (TCP) — IMAPS: IMAP over SSL for secure email access. The most commonly used secure email port today.

File Transfer

• Port 20 (TCP) — FTP Data: FTP data transfer channel.
• Port 21 (TCP) — FTP Control: FTP command channel for file transfers. Insecure; use SFTP instead when possible.
• Port 22 (TCP) — SSH/SFTP: Secure Shell for encrypted remote access and Secure File Transfer. The most important port for server administration.
• Port 69 (UDP) — TFTP: Trivial File Transfer Protocol for simple, lightweight file transfers, commonly used for network device firmware updates.

DNS and Network Services

• Port 53 (TCP/UDP) — DNS: Domain Name System queries and zone transfers. The backbone of internet name resolution.
• Port 67/68 (UDP) — DHCP: Dynamic Host Configuration Protocol for automatic IP address assignment on networks.
• Port 123 (UDP) — NTP: Network Time Protocol for clock synchronization across systems.
• Port 161/162 (UDP) — SNMP: Simple Network Management Protocol for monitoring and managing network devices.

Database and Application Ports

• Port 3306 (TCP) — MySQL/MariaDB: The default port for MySQL and MariaDB database connections.
• Port 5432 (TCP) — PostgreSQL: Default port for PostgreSQL database server.
• Port 27017 (TCP) — MongoDB: Default port for MongoDB NoSQL database.
• Port 6379 (TCP) — Redis: Default port for Redis in-memory data store, widely used for caching.
• Port 5672 (TCP) — RabbitMQ: Default port for RabbitMQ message broker.
• Port 9200 (TCP) — Elasticsearch: Default HTTP port for Elasticsearch search engine.
• Port 3389 (TCP) — RDP: Remote Desktop Protocol for Windows remote access.
• Port 5900 (TCP) — VNC: Virtual Network Computing for remote desktop viewing.

Security Considerations

Understanding ports is essential for network security. Here are key practices:

• Close Unused Ports: Every open port is a potential attack vector. Only keep ports open that are actively serving a purpose. Use firewall rules to block everything else.
• Change Default Ports: Moving services to non-standard ports (like SSH from 22 to a high random port) reduces automated scanning attacks. It's not security by itself, but it reduces noise.
• Use Encrypted Alternatives: Always prefer encrypted port options — HTTPS (443) over HTTP (80), IMAPS (993) over IMAP (143), SSH (22) over Telnet (23). Unencrypted protocols transmit data as plaintext that anyone on the network can read.
• Monitor Port Activity: Regularly scan your systems to identify unexpected open ports. An unexpected open port could indicate a misconfiguration or a compromise. Use the Port Scanner to check your systems.
• Firewall Configuration: Implement both inbound and outbound firewall rules. Inbound rules protect against external attacks. Outbound rules prevent compromised systems from communicating with attackers.

Scanning and Monitoring Ports

Regularly scanning your network ports helps maintain security and identify issues. The Port Scanner on NetTool lets you quickly check the status of any port on any reachable host.

Port states you'll encounter:

• Open: A service is actively accepting connections on this port. Expected for ports running intentional services.
• Closed: The port is reachable but no service is listening. The host responds to connection attempts but refuses them.
• Filtered: A firewall or filter is preventing the scanner from determining the port's state. Connection attempts receive no response at all.

Best practices for port scanning:

1. Scan your own servers regularly to verify only expected ports are open
2. Document which ports should be open on each server and why
3. Set up alerts for unexpected port changes
4. Scan after any configuration changes to verify the effects
5. Only scan systems you own or have explicit permission to test

Frequently Asked Questions

What is a network port?

A network port is a virtual endpoint for network communication. Think of an IP address as a building's street address and ports as individual apartment numbers. Each port number (0-65535) identifies a specific service or application. When data arrives at an IP address, the port number tells the operating system which application should receive it.

What is the difference between TCP and UDP ports?

TCP (Transmission Control Protocol) provides reliable, ordered delivery with error checking and retransmission of lost data. It's used for web browsing, email, and file transfers. UDP (User Datagram Protocol) is faster but less reliable — it sends data without confirming receipt. UDP is ideal for real-time applications like video streaming, gaming, and DNS queries where speed matters more than guaranteed delivery.

How many network ports are there?

There are 65,536 ports (0-65535), divided into three ranges: Well-Known Ports (0-1023) are assigned to common services like HTTP (80) and HTTPS (443). Registered Ports (1024-49151) are assigned to specific applications by IANA. Dynamic/Private Ports (49152-65535) are used temporarily by client applications for outgoing connections.

How do I check if a port is open?

You can check if a port is open using the Port Scanner on NetTool. Enter the target hostname or IP address and the port number(s) you want to check. The tool reports whether each port is open, closed, or filtered. You can also use command-line tools like telnet, nc (netcat), or nmap for local testing.

Why should I close unused ports?

Every open port is a potential entry point for attackers. Unused open ports increase your attack surface without providing any benefit. Closing unnecessary ports reduces the risk of unauthorized access, port-based exploits, and data exfiltration. It's a fundamental security practice to only keep ports open that are actively needed for your running services.