What Port 3373 Is
Port 3373 sits in the registered port range (1024–49151) and is officially assigned by IANA to lavenir-lm — the Lavenir License Manager. It operates on both TCP and UDP.1
The Lavenir License Manager is a network licensing system for Lavenir Technology software. Like most commercial license managers, it works on a client-server model: a license server holds the license pool, clients check out licenses when the software launches, and the manager tracks concurrent usage across a network.
If you've never heard of Lavenir Technology, you're not alone. It's a niche vendor, and port 3373 is the kind of registered port that quietly does its job in the specific environments that need it, invisible everywhere else.
The Registered Port Range
The registered range (1024–49151) is where IANA accepts applications from software vendors who want a permanent, official home for their protocol. Unlike the well-known ports (0–1023) — reserved for foundational Internet services like HTTP, DNS, and SSH — registered ports belong to specific products and platforms.
There are thousands of entries in the registered range. Most of them, like 3373, will never appear in a firewall rule on a general-purpose network. They exist in purpose-built environments: enterprise software deployments, specialized industrial systems, niche professional tools.
That's not a flaw in the port system. It's the system working as designed — a global registry that lets software vendors stake out their own territory without colliding with each other.
If You're Seeing Traffic on Port 3373
A few possibilities:
Lavenir software is actually running. Someone on your network has a Lavenir license server. Check with the team responsible for software licensing.
Something else claimed the port. Applications aren't required to use their registered ports, and nothing prevents unregistered software from binding to 3373. A license manager for different software, a development service, or a misconfigured application could all show up here.
Historical malware association. Port databases note that some older malware used port 3373 for command-and-control traffic. This was opportunistic — attackers pick quiet, unmonitored ports. If you're seeing unexpected traffic here and can't account for it, investigate.2
How to Check What's Listening
On Linux or macOS:
On Windows:
The process ID in the output will tell you exactly what's holding the port open. Cross-reference against your running processes and you'll have your answer quickly.
이 페이지가 도움이 되었나요?