Port 3342: Unassigned — Azure SQL Managed Instance's Public Endpoint

What Range This Port Lives In

Port 3342 is a registered port — the range from 1024 to 49151 that IANA administers for services that have applied for official assignments. Unlike the well-known ports below 1024, registered ports don't require elevated privileges to bind, and not every number in the range has been claimed.

Port 3342 hasn't been. IANA lists it as unassigned.

That doesn't mean it's quiet.

The Real-World Use: Azure SQL Managed Instance

Microsoft chose port 3342 as the public TDS (Tabular Data Stream) endpoint for Azure SQL Managed Instance. When you enable public access on a SQL Managed Instance, it listens on this port. The connection string looks like this:

<instance-name>.public.<dns-zone>.database.windows.net,3342

This is Microsoft's way of letting services outside their virtual network — Power BI, on-premises applications, Azure App Service — reach a managed SQL instance without a VPN.¹

The port is hardcoded. Microsoft's documentation states it plainly: "Port 3342 is used for public endpoint connections to SQL managed instance, and can't be changed currently." ¹

If you're scanning a network and find port 3342 open on an address ending in .database.windows.net, you've found an Azure SQL Managed Instance accepting public connections.

A Note on "WebTIE"

Some port databases list port 3342 as belonging to something called WebTIE. The evidence for this is thin — the name appears in third-party registries without supporting documentation, RFC, or any identifiable product. Treat it as noise.

How to Check What's Listening on This Port

If port 3342 is open on a machine you manage:

On Linux/macOS:

# See what process owns port 3342
sudo ss -tlnp sport = :3342

# Or with lsof
sudo lsof -i :3342

On Windows:

netstat -ano | findstr :3342

The process name will tell you immediately whether it's a SQL service, a custom application, or something unexpected.

Why Unassigned Ports Matter

The registered port range holds 48,128 numbers. Only a fraction have official assignments. The rest are available — legally, by convention — for any application that needs a home.

This is how software actually works. Developers pick numbers that aren't taken (or aren't officially taken), register them if they're building something widely deployed, and sometimes skip registration entirely. IANA's list is aspirational, not comprehensive.

Port 3342 is a small example of the gap between the map and the territory: unassigned on paper, carrying SQL traffic in practice, for thousands of Azure deployments worldwide.