Port 3704: Adobe Server 4 — A Name Without a Tenant

What Port 3704 Is

Port 3704 sits in the registered port range (1024–49151). These ports are assigned by IANA to specific applications and services — not system-level (those are well-known ports below 1024), not ephemeral (those are the temporary high ports above 49151). Registered ports are supposed to mean something.

IANA's registry lists port 3704 as adobeserver-4, registered by Adobe around January 2003, supporting both TCP and UDP.

The Ghost Registration

Here is where it gets honest: Adobe registered a block of ports in the 3701–3704 range (adobeserver-1 through adobeserver-4) in 2003, presumably reserving them for future server software. Then the ports were never used.¹

Adobe's actual Media Server documentation — the product that would most logically claim these ports — lists the ports it uses: 1935 for RTMP, 80 for HTTP, 443 for RTMPS, 1111 for the admin server.² Port 3704 does not appear. Neither does 3701, 3702, or 3703. The registrations exist in the IANA registry. The software doesn't know about them.

This happens more than you'd think. Companies register ports speculatively — for planned products, for features that were never shipped, for software that was eventually sunsetted. IANA doesn't reclaim them. They sit there with names and no tenants.

What You'd Find Here in Practice

Almost certainly nothing official. If something is using port 3704 on a system you're examining, it's not Adobe software. It could be:

• Custom application that chose an obscure registered port deliberately (or accidentally)
• Malware using an unmonitored port that looks legitimate in a port scan
• Misconfigured service that drifted here from a different default

Never assume a port is safe because it has a legitimate-sounding registration. Check what's actually there.

How to Check What's Listening

On Linux or macOS:

sudo ss -tlnp | grep 3704
# or
sudo lsof -i :3704

On Windows:

netstat -ano | findstr :3704

These commands show the process ID of anything bound to the port. From the process ID, you can identify exactly what's running.

Why This Matters

The IANA registry isn't a guarantee of activity — it's a directory of intent. Port 3704 is a useful reminder that a name in a registry and actual network traffic are two different things. When you're auditing a firewall, investigate what's actually listening, not just what the registry says should be there.

If port 3704 shows up open on a machine with no Adobe software installed, that's worth a second look.