Port 3304: OP Session Server — Claimed by a Ghost

What Port 3304 Is

Port 3304 sits in the registered ports range (1024–49151). These ports are not reserved for system services the way well-known ports (0–1023) are, but they are registered with IANA — the Internet Assigned Numbers Authority — to give specific applications a stable, known address.

IANA lists port 3304 as assigned to opsession-srvr, the "OP Session Server." ¹ The registrant on file is Amir Blich at NetManage, a network software company that made remote access and session management tools in the late 1990s and early 2000s. ²

The Service That Was Here

NetManage's OpSession was a remote control product — think early-era remote desktop, before that phrase existed. It let a viewer connect to a host machine over a network or the Internet and observe or control the session. It supported simultaneous multiple viewers, session recording, and integration with NetManage's help desk software. ³

OpSession ran on Windows NT 4.0, Windows 9x, and various UNIX platforms. The standalone viewer also shipped as a plugin for Internet Explorer and Netscape Navigator.

None of this is running anywhere anymore. NetManage has been acquired and absorbed. The product is gone. Port 3304 remains registered in IANA's database because port registrations don't expire automatically — they accumulate.

What This Tells You About the Registry

The registered ports range contains thousands of entries like this: ports claimed by products that once existed, for companies that no longer do. IANA's registry was never designed as a living document with active curation. It's more like a deed archive — once you file, the record persists even if the building burns down.

Port 3304 is not reassigned. It is not in active use for any standard service. If you see traffic on it, it's either:

• A custom application someone chose to run there
• Scanning or probing traffic (port scanners hit everything)
• Malware or unauthorized software (uncommon, but always worth checking)

What's Actually Listening on Your Machine

To see if anything is using port 3304 on your system:

macOS / Linux:

lsof -i :3304

or

ss -tlnp | grep 3304

Windows:

netstat -ano | findstr :3304

If you get no output, nothing is listening. If something shows up, the process name or PID will tell you what it is.