What is the difference between TCP and UDP?

TCP (Transmission Control Protocol) provides reliable, ordered delivery with error checking and retransmission. UDP (User Datagram Protocol) sends packets without guarantees, making it faster but less reliable. HTTP, SSH, and databases use TCP; DNS queries and video streaming often use UDP.

Can two services use the same port?

Not simultaneously on the same IP address and protocol. If port 8080 is already in use by one process, another process cannot bind to the same port. However, different IP addresses on the same machine or different protocols (TCP vs UDP) can share the same port number.

Why does my application use a high-numbered port like 49152?

Ports 49152-65535 are ephemeral (dynamic) ports assigned by your operating system for outbound connections. When your browser connects to a website, the OS picks a random ephemeral port as the source. These ports are automatically released when the connection closes.

How to Look Up Port Numbers

3 min readDevOps

Network ports are the numbered endpoints that allow services to communicate over TCP and UDP. Knowing which port belongs to which service is critical when writing firewall rules, debugging connectivity issues, or auditing server exposure. This guide explains how port numbers work and how to look them up quickly.

Quick Steps

1
Open the Port Reference
Navigate to the Port Reference tool in the DevOps section.
2
Enter a port number or service name
Type the port or service you want to look up in the search bar.
3
View the result
Read the protocol, service name, and description for the matched port.
4
Use the info in your config
Apply the port details to your firewall rules, security groups, or network documentation.

Port Reference

Searchable dictionary of common network ports and services

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How Port Numbers Work

Every network connection uses a port number between 0 and 65535. Ports 0-1023 are 'well-known' ports reserved for standard services like HTTP (80), HTTPS (443), and SSH (22). Ports 1024-49151 are 'registered' ports used by specific applications such as MySQL (3306) or PostgreSQL (5432). Ports 49152-65535 are 'dynamic' or 'ephemeral' ports used temporarily by the operating system for outgoing connections.

Frequently Used Ports

Port    Protocol   Service
──────────────────────────────────
22      TCP        SSH
53      TCP/UDP    DNS
80      TCP        HTTP
443     TCP        HTTPS
3306    TCP        MySQL
5432    TCP        PostgreSQL
6379    TCP        Redis
8080    TCP        HTTP Alternate
8443    TCP        HTTPS Alternate
27017   TCP        MongoDB

Using the Port Reference Tool

Open the Port Reference tool

Navigate to the Port Reference page in the DevOps category.

Search by port number or service name

Type a port number like 5432 to see it maps to PostgreSQL, or type a service name like 'redis' to find port 6379.

Review protocol details

See whether the port uses TCP, UDP, or both, along with the service description and common usage notes.

Security Considerations

Never expose database ports (3306, 5432, 27017) directly to the internet
Use non-standard ports for SSH to reduce automated brute-force attempts
Close all unused ports in your firewall and security groups
Regularly audit listening ports with tools like 'ss -tulnp' or 'netstat -an'

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Frequently Asked Questions

What is the difference between TCP and UDP?: TCP (Transmission Control Protocol) provides reliable, ordered delivery with error checking and retransmission. UDP (User Datagram Protocol) sends packets without guarantees, making it faster but less reliable. HTTP, SSH, and databases use TCP; DNS queries and video streaming often use UDP.
Can two services use the same port?: Not simultaneously on the same IP address and protocol. If port 8080 is already in use by one process, another process cannot bind to the same port. However, different IP addresses on the same machine or different protocols (TCP vs UDP) can share the same port number.
Why does my application use a high-numbered port like 49152?: Ports 49152-65535 are ephemeral (dynamic) ports assigned by your operating system for outbound connections. When your browser connects to a website, the OS picks a random ephemeral port as the source. These ports are automatically released when the connection closes.