What Port 3319 Is
Port 3319 sits in the registered port range (1024–49151). These ports are not reserved for the operating system, but they have been filed with IANA, the organization that keeps track of which services claim which numbers.
The IANA registry lists port 3319 as belonging to SDT License Manager (sdt-lmd), registered to a contact at sdtech@tin.it.1 Tin.it is an Italian ISP that dates to the dial-up era. The registration exists. Evidence of the software it was meant to serve is essentially absent from the modern Internet.
This happens more than you might expect. The registered port range contains thousands of entries from vendors, projects, and software packages that no longer exist or never saw wide adoption. IANA's registry is a historical record as much as it is a living directory.
What You'll Actually Find on This Port
In practice: nothing standard. If something is listening on port 3319 on a machine you control, it's either:
- Custom application software configured to use this port
- A database or service that was moved off its default port (MySQL's default is 3306; some administrators shift replication traffic to avoid conflicts)
- Something that shouldn't be there
One documented edge case: Citrix used the UDP range 3224–3324 for its Framehawk protocol, which carried virtual desktop display traffic between NetScaler Gateway and XenDesktop workers.2 Port 3319 falls inside that range, so Citrix environments may have used it for display traffic. Framehawk has since been deprecated and replaced by EDT (Enlightened Data Transport).
How to Check What's Listening
On Linux or macOS:
On Windows:
The output will show the process ID (PID) and process name of anything bound to the port. If nothing is returned, nothing is listening.
Why Unassigned Ports Matter
The port system works because most software respects the registry. Port 80 is HTTP. Port 443 is HTTPS. Port 22 is SSH. This shared understanding lets firewalls make policy decisions, lets administrators know what to expect, and lets intrusion detection systems flag anomalies.
Unregistered and obscure-registered ports like 3319 are useful precisely because they're quiet. An application that needs a non-standard port often picks from this range to avoid collisions. The fact that nothing well-known lives here makes it easy to spot if something unexpected shows up.
A port that should be empty and isn't is worth investigating.
此页面对您有帮助吗？