Port 3447: DirectNet — A Peer-to-Peer IM Experiment That Time Forgot

What Port 3447 Is

Port 3447 sits in the registered port range — the block from 1024 to 49151 that IANA manages for specific services. Any application or organization can apply to claim a port in this range, and IANA will record the assignment. Unlike the well-known ports below 1024, registered ports don't require elevated system privileges to open. They're the middle ground between reserved infrastructure and free-for-all.

In 2002, IANA registered port 3447 for DirectNet, an instant messaging protocol developed by Gregor Richards and documented as "CDDN" (CompuDuo DirectNet). ¹

What DirectNet Was

Most instant messaging of that era — AIM, MSN Messenger, ICQ — worked by routing your messages through central servers. You sent a message to AOL's infrastructure, AOL's infrastructure forwarded it to your friend. The company in the middle saw everything.

DirectNet tried something different: skip the middleman entirely. Messages would travel directly between users, peer-to-peer, without any central relay. No server holding your conversation. No company logging your chats.

It was a genuinely interesting idea. It was also abandoned before it mattered. The protocol never achieved significant adoption, the project faded from active development, and port 3447 became a registration without a constituency. ²

What's Actually on Port 3447 Today

Probably nothing, or something unrelated to DirectNet. When a registered port belongs to a dead protocol, it becomes available real estate for anything: development servers, internal tools, proprietary software, or simply nothing at all.

The IANA registration remains on the books, but "registered" doesn't mean "actively used." It means someone once filed the paperwork.

How to Check What's Using Port 3447

If you see port 3447 active on your system or network, you can find out what's there:

On Linux or macOS:

# Show the process listening on port 3447
sudo ss -tlnp | grep 3447
# or
sudo lsof -i :3447

On Windows:

# Show process ID for port 3447
netstat -ano | findstr :3447
# Then look up the process ID in Task Manager

Why Unassigned Ports Matter

The registered port range has 48,128 slots. IANA has assigned only a fraction of them. The rest are blank canvas — available for applications, experiments, and internal services to use without coordination.

This matters because port numbers are how operating systems and firewalls make routing decisions. When you open port 3447 in a firewall rule, you're trusting that whatever runs there is what you intended. An unassigned port doesn't announce itself. It doesn't carry a label. You have to know what you put there.

The DirectNet registration is a mild footnote: if you're building something that needs a port and you want to avoid conflicts with documented services, checking IANA's registry first costs nothing. ³