Port 836: Unassigned — A gap in the well-known range

Port 836 is unassigned. It has no official service, no protocol, no RFC defining its purpose. And yet it sits in the well-known ports range (0-1023)—the space reserved for fundamental Internet services like HTTP, DNS, and SSH.¹

What the Well-Known Range Means

Ports 0-1023 are called well-known ports or system ports. On most operating systems, only privileged processes can bind to these ports. They're meant for services so essential that they need special protection.²

Port 80 is in this range (HTTP). Port 22 is here (SSH). Port 53 is here (DNS). These are services the Internet can't function without.

Port 836 is also here. But it carries nothing.

Why Unassigned Ports Exist

IANA doesn't assign all 1024 well-known port numbers. Some are left unassigned deliberately—reserved for future protocols that might need them. Port 836 is one of these gaps.³

According to the IANA registry, ports 834-846 are marked as "Unassigned" for both TCP and UDP. That's a block of 13 consecutive ports with no official purpose.

No Unofficial Uses Either

Unlike some unassigned ports that get repurposed by applications (BitTorrent, gaming servers, custom protocols), port 836 doesn't have any commonly observed unofficial uses. It's not just officially empty—it's practically empty too.

If you see traffic on port 836, it's either:

• A custom application someone configured to use this port
• Malware trying to hide in an obscure port number
• A misconfiguration

How to Check What's Using Port 836

On Linux or macOS:

sudo lsof -i :836
# or
sudo netstat -tulpn | grep :836

On Windows:

netstat -ano | findstr :836

If something is listening on this port, you'll see the process ID (PID) and can investigate what application it belongs to.

Why This Matters

The existence of unassigned ports like 836 shows something important about how the Internet works: not everything is planned. The well-known range was allocated decades ago, and IANA assigned ports conservatively—they didn't fill every slot.

This means there's room. Room for future protocols no one has imagined yet. Room for the next fundamental service that will need a port number and privileged access.

Port 836 is waiting. It might wait forever, or it might become as essential as port 80 is today. Right now, it's just a number—reserved, protected, and unused.