Port 2399: FileMaker Data Access — The ODBC/JDBC Door That Doesn't Move

What Port 2399 Is

Port 2399 is the registered home of fmpro-fdal — FileMaker, Inc.'s Data Access Layer. It's the port FileMaker Server listens on for ODBC and JDBC connections, and it cannot be changed.¹

That last part is worth pausing on. Most server software lets you configure which port it uses. FileMaker doesn't give you that option for ODBC/JDBC. Port 2399 is it. Every third-party tool that wants to query a FileMaker database as a data source — a reporting engine, a spreadsheet, an ETL pipeline, a custom application — connects on port 2399, full stop.²

What the Port Range Means

Port 2399 sits in the registered port range (1024–49151). These ports are assigned by IANA to specific services but don't require elevated privileges to use, unlike the well-known ports below 1024. Registered doesn't mean mandatory — plenty of registered ports go unused on most systems. But it does mean there's an official record: this port belongs to FileMaker's data layer.³

What ODBC/JDBC Actually Does Here

ODBC (Open Database Connectivity) and JDBC (Java Database Connectivity) are standard interfaces that let applications treat a database as a data source regardless of the underlying engine. FileMaker implements both, exposing its proprietary database format to any tool that speaks these standards.

When a client connects via ODBC or JDBC, it reaches FileMaker Server on port 2399. The server authenticates the request, runs the query against the FileMaker database, and returns results in a format the client understands. This is how a tool like Tableau, Crystal Reports, or even Microsoft Excel can pull live data out of a FileMaker database.

Security Considerations

Some port-scanning tools and firewall advisories flag port 2399 as "associated with malware." This warning deserves skepticism. Nearly every port number has been used by something malicious at some point — that's not a meaningful distinction. If you're running FileMaker Server and have intentionally opened port 2399 for ODBC/JDBC access, the risk profile is the same as any database port exposed to a network: strong authentication matters, network-level access controls matter, and exposing it to the open Internet without a VPN is inadvisable.⁴

If you're not running FileMaker and see something listening on port 2399, that's worth investigating.

How to Check What's Listening

macOS/Linux:

sudo lsof -i :2399
# or
sudo ss -tlnp | grep 2399

Windows (Command Prompt, run as Administrator):

netstat -ano | findstr :2399

The output will show the process ID. On macOS/Linux, lsof will show the process name directly.