What is the difference between TCP and UDP?

TCP (Transmission Control Protocol) is connection-oriented and ensures reliable, ordered delivery of data with error checking and retransmission. UDP (User Datagram Protocol) is connectionless and faster but does not guarantee delivery or order. TCP is used for applications requiring reliability (web, email, file transfer), while UDP is used for real-time applications (streaming, gaming, DNS) where speed is more important than perfect reliability.

What are well-known ports?

Well-known ports (0-1023) are assigned by IANA (Internet Assigned Numbers Authority) for standard services and protocols. Examples include port 80 for HTTP, 443 for HTTPS, 22 for SSH, and 25 for SMTP. These ports require system/root privileges to bind on Unix-like systems and are standardized globally.

What ports should never be exposed to the internet?

Critical ports that should never be exposed include: database ports (3306/MySQL, 5432/PostgreSQL, 1433/SQL Server, 27017/MongoDB, 6379/Redis), remote desktop (3389/RDP, 5900/VNC), file sharing (445/SMB, 139/NetBIOS), and management interfaces (Docker API, Kubernetes API). Always use firewalls, VPNs, or SSH tunnels to access these services.

How do I scan for open ports on my system?

Use tools like nmap ("nmap localhost" or "nmap [IP]"), netstat ("netstat -tuln" on Linux/Mac, "netstat -ano" on Windows), or ss ("ss -tuln" on Linux). For cloud instances, use your provider's security group analyzer or third-party scanning services. Always get permission before scanning systems you don't own.

What is port forwarding?

Port forwarding redirects network traffic from one port to another, often from a public IP address to a private internal network address. It's commonly used to allow external access to services behind a router/firewall (e.g., hosting a web server, remote desktop, gaming server). Configure it carefully as it can expose internal services to the internet.

Why are some ports marked as dangerous?

Ports are marked dangerous when: they lack encryption (FTP, Telnet, HTTP), have known vulnerabilities, are frequently targeted by attackers, expose sensitive services (databases, management interfaces), or use outdated protocols. Modern alternatives exist for most dangerous ports (SSH instead of Telnet, HTTPS instead of HTTP, SFTP instead of FTP).

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Network Port Reference

Comprehensive database of 5,900+ network ports, protocols, and services. Search by port number, service name, or category to find detailed information and security recommendations.

Ethical Use Notice

This tool is provided for educational, defensive security, and authorized testing purposes only. Unauthorized access to computer systems, networks, or data is illegal. Always obtain proper authorization before conducting security assessments or testing. Use this tool responsibly and in compliance with all applicable laws and regulations.

Reference Database

This tool provides information about common network ports and their services. To scan for open ports on a system, use tools like nmap, netstat, or specialized network scanners.

Search by port, service, or description

Category

Protocol

Showing 5986 of 5986 ports

Per page:

Port	Protocol	Service	Description	Category	Security
1	Both	tcpmux	Multiplexer	Other	Configure firewall rules and authentication appropriately.
5	Both	rje	Entry	Other	Configure firewall rules and authentication appropriately.
7	Both	echo	Echo	Network	Configure firewall rules and authentication appropriately.
9	Both	discard	Discard	Network	Configure firewall rules and authentication appropriately.
11	Both	systat	Users	Other	Configure firewall rules and authentication appropriately.
13	Both	daytime	Daytime	Network	Configure firewall rules and authentication appropriately.
17	Both	qotd	Day	Network	Configure firewall rules and authentication appropriately.
18	Both	msp	(historic)	Other	Configure firewall rules and authentication appropriately.
19	Both	chargen	Generator	Network	Configure firewall rules and authentication appropriately.
20	Both	ftp-data	Data]	File Transfer	Configure firewall rules and authentication appropriately.
21	Both	ftp	[Control]	File Transfer	🟡 Unencrypted. Use encrypted alternative or VPN. Restrict network access.
22	Both	ssh	Protocol	File Transfer	🟢 Encrypted protocol. Ensure strong cipher suites and valid certificates.
23	Both	telnet	Telnet	Remote Access	🔴 Critical risk. Frequently exploited. Never expose to internet.
25	Both	smtp	Transfer	Mail	🟡 Unencrypted. Use encrypted alternative or VPN. Restrict network access.
27	Both	nsw-fe	FE	Other	Configure firewall rules and authentication appropriately.
29	Both	msg-icp	ICP	Other	Configure firewall rules and authentication appropriately.
31	Both	msg-auth	Authentication	Other	Configure firewall rules and authentication appropriately.
33	Both	dsp	Protocol	Other	Configure firewall rules and authentication appropriately.
37	Both	time	Time	Time	Configure firewall rules and authentication appropriately.
38	Both	rap	Protocol	Other	Configure firewall rules and authentication appropriately.
39	Both	rlp	Protocol	Other	Configure firewall rules and authentication appropriately.
41	Both	graphics	Graphics	Other	Configure firewall rules and authentication appropriately.
42	Both	name	Server	Other	Configure firewall rules and authentication appropriately.
43	Both	nicname	Is	Other	Configure firewall rules and authentication appropriately.
44	Both	mpm-flags	Protocol	Other	Configure firewall rules and authentication appropriately.
45	Both	mpm	[recv]	Other	Configure firewall rules and authentication appropriately.
46	Both	mpm-snd	send]	Other	Configure firewall rules and authentication appropriately.
48	Both	auditd	Daemon	Other	Configure firewall rules and authentication appropriately.
49	Both	tacacs	(TACACS)	Other	Configure firewall rules and authentication appropriately.
50	Both	re-mail-ck	Protocol	Mail	Configure firewall rules and authentication appropriately.
52	Both	xns-time	Protocol	Time	Configure firewall rules and authentication appropriately.
53	Both	domain	Server	DNS	Configure firewall rules and authentication appropriately.
54	Both	xns-ch	Clearinghouse	Other	Configure firewall rules and authentication appropriately.
55	Both	isi-gl	Language	Other	Configure firewall rules and authentication appropriately.
56	Both	xns-auth	Authentication	Other	Configure firewall rules and authentication appropriately.
58	Both	xns-mail	Mail	Mail	Configure firewall rules and authentication appropriately.
62	Both	acas	Services	Other	Configure firewall rules and authentication appropriately.
63	Both	whoispp	whois++	Other	Configure firewall rules and authentication appropriately.
64	Both	covia	(CI)	Other	Configure firewall rules and authentication appropriately.
65	Both	tacacs-ds	Service	Other	Configure firewall rules and authentication appropriately.
66	Both	sql-net	SQL*NET	Database	Configure firewall rules and authentication appropriately.
67	Both	bootps	Server	Network	Configure firewall rules and authentication appropriately.
68	Both	bootpc	Client	Network	Configure firewall rules and authentication appropriately.
69	Both	tftp	Transfer	File Transfer	🟡 Unencrypted. Use encrypted alternative or VPN. Restrict network access.
70	Both	gopher	Gopher	Other	Configure firewall rules and authentication appropriately.
71	Both	netrjs-1	Service	Other	Configure firewall rules and authentication appropriately.
72	Both	netrjs-2	Service	Other	Configure firewall rules and authentication appropriately.
73	Both	netrjs-3	Service	Other	Configure firewall rules and authentication appropriately.
74	Both	netrjs-4	Service	Other	Configure firewall rules and authentication appropriately.
76	Both	deos	Store	Other	Configure firewall rules and authentication appropriately.

Page 1 of 120

Security Indicator Legend

Green: Secure/Encrypted

Yellow: Conditional Security

Red: Critical/Dangerous

Gray: Unknown/Not in DB

Common Port Groups

Security Best Practices

•Never expose database ports (3306, 5432, 1433, 27017, 6379) to the internet. Use SSH tunnels or VPNs.
•Disable legacy protocols like Telnet (23), FTP (21), and HTTP (80) in favor of encrypted alternatives.
•Use firewalls to restrict access to only necessary ports and trusted IP addresses.
•Enable authentication on all services, especially those that default to no auth (Redis, Memcached, MongoDB).
•Regularly audit open ports using tools like nmap, netstat, or ss to identify unexpected services.

Understanding Network Ports

Network ports are virtual endpoints for communication in computer networks. Think of them as doors through which data enters and leaves a computer. Each port is identified by a number (0-65535) and associated with specific protocols and services.

Well-Known Ports

Ports 0-1023

• Assigned by IANA
• Standard services
• Require elevated privileges
• Examples: HTTP (80), HTTPS (443)

Registered Ports

Ports 1024-49151

• Registered with IANA
• User-level applications
• Vendor-specific services
• Examples: MySQL (3306), PostgreSQL (5432)

Dynamic/Private Ports

Ports 49152-65535

• Ephemeral ports
• Temporary client connections
• Private/custom services
• Assigned dynamically by OS

Common Network Protocols

TCPTransmission Control Protocol

Connection-oriented protocol that ensures reliable, ordered delivery of data with error checking and automatic retransmission.

Characteristics:

Three-way handshake (SYN, SYN-ACK, ACK)
Guaranteed delivery and order
Flow control and congestion control
Higher overhead, slower than UDP

Common Uses: Web browsing (HTTP/HTTPS), email (SMTP, IMAP), file transfer (FTP, SFTP), remote access (SSH, RDP)

UDPUser Datagram Protocol

Connectionless protocol that sends data without establishing a connection or guaranteeing delivery. Faster but less reliable than TCP.

Characteristics:

No connection establishment
No delivery guarantee or ordering
No flow or congestion control
Lower overhead, faster than TCP

Common Uses: DNS queries, video/audio streaming, online gaming, VoIP, DHCP, NTP (time sync)

Most Commonly Used Ports

80

TCP

HTTP - Web Traffic

Hypertext Transfer Protocol for unencrypted web browsing. Deprecated in favor of HTTPS (port 443).

Unencrypted - use HTTPS instead

443

TCP

HTTPS - Secure Web

HTTP over TLS/SSL for encrypted web browsing. Standard for all modern websites.

Encrypted and secure

22

TCP

SSH - Secure Shell

Encrypted remote access and secure file transfer. Use key-based authentication.

Secure with proper config

3306

TCP

MySQL Database

MySQL/MariaDB database server. Never expose to the internet.

Never expose publicly

5432

TCP

PostgreSQL Database

PostgreSQL database server. Use SSH tunnels or VPNs for remote access.

Never expose publicly

53

Both

DNS - Domain Name System

Translates domain names to IP addresses. UDP for queries, TCP for zone transfers.

Essential network service

Quick Port Lookup Tips

•Use the search box above to find any port by number, service name, or description
•Filter by category (Web, Database, Mail, etc.) to browse related services
•Filter by protocol (TCP, UDP, or Both) to narrow your search
•Pay attention to security indicators - red means never expose, yellow means conditional, green means generally secure

Port Security Best Practices

Never Expose to Internet

•
Database Ports: MySQL (3306), PostgreSQL (5432), MongoDB (27017), Redis (6379), SQL Server (1433)
•
Remote Desktop: RDP (3389), VNC (5900)
•
File Sharing: SMB (445), NetBIOS (139)
•
Management Interfaces: Docker API (2375/2376), Kubernetes API (6443)

Security Best Practices

•
Use Firewalls: Configure strict ingress/egress rules. Allow only necessary ports from trusted IPs.
•
Encrypt Everything: Use TLS/SSL for all services. Replace HTTP with HTTPS, FTP with SFTP, Telnet with SSH.
•
Use VPNs/Tunnels: Access internal services through VPN or SSH tunnels instead of exposing ports.
•
Regular Audits: Use nmap, netstat, or ss to scan for unexpected open ports regularly.

Common Attack Vectors

Port Scanning: Attackers scan for open ports to identify services and potential vulnerabilities. Use intrusion detection systems (IDS) to detect scanning activity.

Service Exploitation: Once open ports are found, attackers attempt to exploit known vulnerabilities in the services running on those ports. Keep all services updated.

Brute Force Attacks: Services like SSH (22), RDP (3389), and FTP (21) are common targets for password guessing. Use key-based authentication and rate limiting.

DDoS Amplification: Open DNS (53), NTP (123), and SNMP (161) services can be abused for reflection attacks. Configure services to only respond to trusted sources.

Frequently Asked Questions

Find answers to common questions

A network port is a virtual point where network connections start and end. Ports are identified by numbers (0-65535) and associated with specific protocols (TCP or UDP). They allow a single computer to handle multiple network services simultaneously by directing traffic to the appropriate application or service.

Key Security Terms

Understand the essential concepts behind this tool

View all terms in our glossary →

🌐

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Network Port Reference

Ethical Use Notice

Security Indicator Legend

Common Port Groups

Security Best Practices

Understanding Network Ports

Well-Known Ports

Registered Ports

Dynamic/Private Ports

Common Network Protocols

TCPTransmission Control Protocol

UDPUser Datagram Protocol

Most Commonly Used Ports

80

443

22

3306

5432

53

Quick Port Lookup Tips

Port Security Best Practices

Never Expose to Internet

Security Best Practices

Common Attack Vectors

Frequently Asked Questions

Key Security Terms

MAC Address

Port Numbers

Subnet Mask

Penetration Testing

Subnet Calculator

DNS Lookup

IP Address Lookup

Need Help with Network Security?

Network Port Reference

Ethical Use Notice

Security Indicator Legend

Common Port Groups

Security Best Practices

Understanding Network Ports

Well-Known Ports

Registered Ports

Dynamic/Private Ports

Common Network Protocols

TCPTransmission Control Protocol

UDPUser Datagram Protocol

Most Commonly Used Ports

80

443

22

3306

5432

53

Quick Port Lookup Tips

Port Security Best Practices

Never Expose to Internet

Security Best Practices

Common Attack Vectors

Frequently Asked Questions

Key Security Terms

MAC Address

Port Numbers

Subnet Mask

Penetration Testing

Related Network Tools

Subnet Calculator

DNS Lookup

IP Address Lookup

Need Help with Network Security?