Port 20036: Unassigned — An Empty Address in the Internet's Directory

Port 20036 has no official assignment from IANA (Internet Assigned Numbers Authority). It's one of tens of thousands of ports in the registered range that currently carry no standard protocol, no well-known service, no RFC defining their purpose.¹

The Registered Ports Range

Port 20036 lives in the registered ports range (1024-49151). This is the middle territory of the port number space:

• Well-known ports (0-1023): Reserved for standard protocols like HTTP, SSH, DNS
• Registered ports (1024-49151): Available for registration with IANA for specific services
• Dynamic/ephemeral ports (49152-65535): Used temporarily for client-side connections

The registered range contains 48,128 possible port numbers. Only a fraction have official assignments. The rest, like port 20036, remain unassigned — available for anyone who needs them.²

What This Means

An unassigned port can be used by:

• Custom applications that need a network endpoint
• Internal services within an organization
• Development and testing environments
• Any software that doesn't conflict with well-known services

There's no central authority stopping you from using port 20036. You just won't find it in /etc/services or documented in an RFC.

Checking What's Listening

If you need to see what (if anything) is using port 20036 on your system:

On Linux/macOS:

# See what's listening on port 20036
sudo lsof -i :20036

# Or using netstat
sudo netstat -tulpn | grep 20036

# Or using ss (modern alternative)
ss -tulpn | grep 20036

On Windows:

# Show connections on port 20036
netstat -ano | findstr :20036

If nothing returns, the port is unused. If something does, you've found what claimed this empty address.

Why Unassigned Ports Matter

The Internet's port system works because most of the address space is empty. The 48,128 registered ports give applications room to breathe — space to claim a number without stepping on SSH (22) or HTTPS (443) or the thousand other services people depend on.

Port 20036 is infrastructure by virtue of being available. It's a parking space, an empty lot, a number waiting in the directory for someone who needs it.

Most ports are like this. Quiet. Unassigned. Ready.