Random Port Number Generator

How to use

1. 1️⃣
   Choose your options above
2. 2️⃣
   Click Generate
3. 3️⃣
   Copy your result

Detailed instructions

1. Set the Count field to how many port numbers you need, from 1 up to 50.
2. Choose a Port Range from the dropdown: well-known (0-1023), registered (1024-49151), or dynamic (49152-65535).
3. Click Generate to produce a list of random port numbers, each labeled with a service name if one is recognized.
4. Review the results and discard any labeled ports that conflict with services already running on your system.
5. Copy the remaining ports directly into your config file, test script, or firewall rule definition.

Use Cases

• •Picking non-conflicting ports for services in a docker-compose.yml on a shared dev machine
• •Generating a pool of registered-range ports to populate firewall ACL test cases
• •Filling a network topology diagram in draw.io with plausible service port assignments
• •Seeding socket-handling fuzz tests in Go or Rust with varied port values across all ranges
• •Reserving ephemeral port candidates for a Kubernetes sidecar proxy without hitting common service ports

Tips

• →Stick to the dynamic range (49152-65535) for throwaway test servers — OS processes rarely hold these ports long-term.
• →If you need ports that are guaranteed unknown services, generate from the registered range and re-run until you get a batch with no service labels.
• →Cross-reference results with `ss -tuln` on Linux or `netstat -ano` on Windows before assigning them to a long-running process.
• →For docker-compose files, generate 5-10 registered-range ports at once and map one per service to avoid hard-coding common defaults like 8080 or 3000.
• →When simulating port scans in a lab, mix all three ranges to create a realistic distribution that mirrors what a real host exposes.
• →Avoid ports ending in 00 or 000 (8000, 9000, 3000) even if unlabeled — these are conventions many tools default to, so collisions are common in shared dev environments.

FAQ