What Port 2807 Is
Port 2807 sits in the registered port range (1024–49151). These ports are registered with IANA — the Internet Assigned Numbers Authority, the body that keeps the global port directory — but they don't carry the same universal recognition as well-known ports like 80 (HTTP) or 443 (HTTPS).
IANA lists port 2807 under the service name cspmulti, on both TCP and UDP. The assignee is a contact at pfu.co.jp — PFU Limited, the Japanese IT company known for the Fujitsu ScanSnap document scanner line, the Happy Hacking Keyboard, and enterprise IT infrastructure. PFU was a Fujitsu subsidiary for decades before Ricoh acquired it in 2022.
Beyond the registry entry, there is no public documentation. No RFC, no developer guide, no forum thread that explains what cspmulti actually does. It was registered, and then went quiet.
What "Registered" Means Here
The registered range exists for applications that need a consistent, predictable port — so that clients know where to connect without negotiating. Any company or developer can submit a registration request to IANA. Many do. Most registered services are niche, proprietary, or simply internal tools that were assigned a port to avoid collisions with other software.
The key distinction from well-known ports (0–1023): registered ports don't require elevated OS privileges to bind on most systems. Any process can listen on 2807 without administrator rights.
What Might Actually Be on Port 2807
If you see port 2807 open on a system, it is almost certainly not cspmulti. More likely:
- PFU scanner or keyboard software running a local management service (if PFU software is installed)
- A development server that happened to pick this port
- Application-assigned ephemeral use — some software picks registered ports for temporary connections
No known malware families are associated with this port.
How to Check What's Listening
On Linux or macOS:
On Windows:
The output will show the process ID. You can then look up that PID in Task Manager (Windows) or with ps aux | grep <PID> (Linux/macOS) to identify what's actually running there.
Why Unassigned-in-Practice Ports Matter
The port registry has over 49,000 registered ports. Most software doesn't check the registry before picking a port — it just needs a number that isn't already in use. This means port 2807 could show up on any system for any reason, with cspmulti being the official name but an entirely unrelated process being the actual occupant.
This is normal. The registry prevents well-known collisions; it doesn't govern every connection on every machine. If you see 2807 open and don't recognize the process, the lsof or netstat commands above will tell you the truth.
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