Port 20035: Unassigned — A Blank Space in the Registry

Port 20035 has no official assignment. No RFC defines what should run here. No IANA registration claims this number. It's a blank space in the registry.

The Registered Port Range

Port 20035 falls in the registered port range (1024-49151). This is the middle territory of the port system:

• Well-known ports (0-1023): Require root privileges, reserved for core Internet services
• Registered ports (1024-49151): Available for applications to register with IANA on a first-come, first-served basis
• Dynamic/ephemeral ports (49152-65535): Temporary ports assigned automatically by your operating system

Any application can request to register a port in this range through IANA. Many do. Most don't. The registered range is mostly empty — nearly 50,000 port numbers, and only a fraction have official assignments.¹

Why Unassigned Ports Matter

Unassigned ports serve three purposes:

1. Room for growth
New protocols and services emerge constantly. The Internet needs unclaimed port numbers for them to use.

2. Private applications
Your company's internal tools, your personal projects, experimental software — they all need ports. Unassigned numbers give developers space to build without colliding with official assignments.

3. Flexibility
Not everything needs to be registered. If your application only runs on your own network, you can use any unassigned port. Registration matters when you need global coordination — when thousands of different networks need to know "service X always uses port Y."

What Might Be Using Port 20035

On your system right now, port 20035 might be:

• Nothing — Most ports sit unused most of the time
• A custom application — Internal tools often grab random unassigned ports
• Malware — Unassigned ports are sometimes used by trojans precisely because they're not monitored²
• Temporary assignment — Your OS might assign it as an ephemeral port for an outgoing connection

How to Check What's Listening

On Linux/macOS:

# See all listening ports with process names
sudo lsof -i -P -n | grep LISTEN

# Check a specific port
sudo lsof -i :20035

# Using netstat (older but widely available)
sudo netstat -tulpn | grep 20035

On Windows:

# See all listening ports
netstat -ano | findstr LISTENING

# Check a specific port
netstat -ano | findstr :20035

The output shows you the process ID (PID) and program name. If nothing appears, the port is not in use.³

The Truth About Empty Ports

The registered port range is mostly silence. Out of nearly 50,000 available numbers, only a few thousand have official assignments. The rest — ports like 20035 — sit waiting.

Some will eventually be claimed by new protocols. Some will be used temporarily by applications that come and go. Most will remain empty indefinitely.

This emptiness is not waste. It's capacity. The Internet was designed with room to grow, and unassigned ports are part of that design. They're the blank pages in a book that's still being written.