Port 819 — Unassigned

Port 819 has no official service assigned to it.

What This Port Is

Port 819 falls within the well-known ports range (0-1023)—the first 1,024 port numbers reserved by the Internet Assigned Numbers Authority (IANA) for system services and core Internet protocols.¹

But unlike port 22 (SSH) or port 443 (HTTPS), port 819 has never been claimed. No RFC defines it. No protocol runs on it. No service waits there by default.

Why Ports Stay Unassigned

The well-known range contains 1,024 port numbers. Only about 300 of them have official assignments.² The rest—like port 819—remain unassigned for a few reasons:

Reserved for future use — IANA keeps numbers available so new protocols can claim well-known ports when needed.

Historical artifacts — Some ports were reserved decades ago for services that never gained traction or were abandoned.

No one asked — Getting a well-known port requires IETF review or IESG approval.³ If no one ever submitted a proposal for port 819, it stays empty.

What Might Be Using It Anyway

Just because a port is unassigned doesn't mean nothing is listening there. Applications can bind to any port they want, official assignment or not.

Check what's listening on your system:

# Linux/macOS - see what's using port 819
sudo lsof -i :819
sudo netstat -tulpn | grep :819

# Windows - check port 819
netstat -ano | findstr :819

If nothing returns, the port is closed. If something appears, you're looking at an application that chose port 819 for its own reasons—maybe a custom service, a corporate app, or malware.

Security Note

Unassigned ports in the well-known range are sometimes used by attackers precisely because they're unexpected. If you find traffic on port 819 and you didn't configure anything to use it, investigate.

Most firewalls block inbound traffic to unassigned well-known ports by default. That's good practice.

Why Unassigned Ports Matter

The existence of unassigned ports shows how the Internet reserves space for evolution. Not every number needs to be claimed right now. The architecture leaves room for protocols that haven't been invented yet.

Port 819 might stay empty forever. Or someday, an RFC will assign it to a service that becomes essential. Until then, it waits.

Related Ports

• Port 0 — Reserved, cannot be used
• Ports 1-1023 — Well-known ports range (where 819 lives)
• Ports 1024-49151 — Registered ports (require IANA registration but less strict)
• Ports 49152-65535 — Dynamic/ephemeral ports (used temporarily by applications)