What This Port Is
Port 3372 has no official IANA service assignment. It sits in the registered port range (1024–49151), the space where applications can stake a claim with IANA, but no service has formally done so here.
That doesn't mean the port is empty. Port 3372 has a well-documented unofficial life as the home of TIP — the Transaction Internet Protocol — as implemented by Microsoft's Distributed Transaction Coordinator (MSDTC).
The Registered Port Range
Ports 1024 through 49151 are registered ports. Unlike the well-known ports (0–1023), they don't require elevated system privileges to open, and IANA maintains a registry of which services have claimed which numbers. Port 3372 appears in that registry's gaps — claimed in practice by certain Windows infrastructure, but never formally assigned.
The Unofficial Resident: MSDTC and TIP
MSDTC (Microsoft Distributed Transaction Coordinator) is the Windows service responsible for coordinating transactions that span multiple databases, message queues, or other resource managers. When a transaction touches a SQL Server on machine A and a message queue on machine B, something has to ensure that both sides either commit or roll back together. That something is MSDTC.
The protocol it uses for cross-machine coordination is TIP — Transaction Internet Protocol. Port 3372 is where TIP listens.
The problem TIP solves is genuinely hard: two databases need to agree that a transaction succeeded, but either machine can crash before the confirmation arrives. TIP implements a two-phase commit — a prepare phase where both sides signal readiness, and a commit phase where the coordinator confirms. Port 3372 is the channel for that conversation.1
Some older Windows security databases and port scanners also list port 3372 under the service name tip2, reflecting an earlier draft version of the protocol.
Security Considerations
MSDTC has historically been a source of remote code execution vulnerabilities on Windows systems.2 If port 3372 is open on a machine not intended to run MSDTC, that's worth investigating. The service is sometimes enabled by default on Windows Server installations even when not needed.
What's Listening on This Port
To check what process is using port 3372 on your system:
Windows:
Linux / macOS:
Cross-platform (nmap):
If MSDTC is running and you see port 3372 open, that's expected Windows behavior. If you're not running distributed transactions, disabling MSDTC is a reasonable security hardening step.
Why Unassigned Ports Matter
The gap between what IANA officially assigns and what software actually uses is real and large. Thousands of ports in the registered range carry traffic from software that never filed paperwork with IANA. Port 3372 is a mild example: Microsoft used it for decades without a formal registration.
This matters for firewall rules, security auditing, and network monitoring. An "unassigned" port isn't necessarily an empty one — it might be carrying infrastructure your systems depend on, or it might be carrying something you'd rather not have there at all. The only way to know is to look.
Ήταν χρήσιμη αυτή η σελίδα;