Port 2100 does not appear in the IANA service registry with an assigned owner. But that doesn't mean it's empty — it means its primary occupant moved in without filing paperwork.
The Oracle XML DB Connection
Oracle XML DB, introduced in Oracle 9i (2001), gave the Oracle database its own built-in HTTP and FTP servers. The idea was to expose a hierarchical XML repository directly inside the database, accessible via standard Internet protocols without a separate middleware layer.
Oracle needed FTP to run on a non-standard port — regular port 21 requires root privileges on Unix systems, and running the Oracle database as root is not something any DBA wants to do. So Oracle picked port 2100 as its default FTP port, and port 8080 for HTTP.1
The result: on any Oracle 9i, 10g, 11g, or later database with XML DB installed and FTP enabled, port 2100 is where the FTP server listens. That covers a substantial portion of Oracle installations worldwide.
This is how port usage actually works in practice. Official IANA registration matters, but software ships with defaults, defaults become conventions, and conventions become de facto standards — whether IANA is involved or not.
What Range This Port Belongs To
Port 2100 falls in the registered port range: 1024–49151.
These ports are not as tightly controlled as the well-known ports (0–1023), which require elevated privileges to bind on most operating systems. Registered ports can be bound by any process with sufficient permissions, and IANA maintains a voluntary registry of assignments. But "unassigned" in this range simply means nobody formally registered it — not that nobody uses it.
How to Check What's Listening on Port 2100
If you want to know whether anything is listening on port 2100 on your system:
On macOS or Linux:
Or:
On Windows:
If Oracle XML DB is running with FTP enabled, you'll see it here. If nothing appears, the port is idle.
Security Note
Oracle XML DB's FTP server sends passwords in cleartext — that's the nature of the FTP protocol. Oracle's own documentation notes that FTP is disabled by default for this reason.2 If you see something listening on port 2100 on an Oracle database, verify whether FTP access is intentional and whether the database is exposed beyond your local network.
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