Port 1748 sits in the registered ports range (1024–49151), the middle tier of the port numbering system. These ports don't require root or administrator privileges to bind, and they're allocated by IANA upon application from software vendors.
IANA registered this port as oracle-em1 — the first Oracle Enterprise Manager port designation. In practice, it serves as the default gateway proxy port for Oracle Enterprise Manager Cloud Control in hybrid cloud configurations.
What It Does
Oracle Enterprise Manager Cloud Control manages Oracle databases across on-premises and cloud environments from a single console. When an organization runs databases in Oracle Cloud while managing them from on-premises infrastructure, the two sides need a communication channel. Port 1748 is that channel by default.
The Gateway Proxy sits between cloud-based database agents and the on-premises Oracle Management Service (OMS). Traffic flows through this port in both directions: commands going out to cloud agents, monitoring data and alerts coming back in.
If port 1748 is unavailable when Enterprise Manager starts, it doesn't fail — it quietly tries ports 1830 through 1848 until it finds one that's free. Most Oracle DBAs configuring firewalls for hybrid cloud deployments need to allow the entire range, not just 1748.
Who Uses It
This is Oracle-specific infrastructure. If you see traffic on port 1748, it's almost certainly an Oracle Enterprise Manager installation running hybrid cloud management. It won't appear on systems without Oracle software.
How to Check What's Listening
On Linux/macOS:
On Windows:
If something is listening, the process name will tell you whether it's Oracle EM or something else.
Why Unassigned and Registered Ports Matter
The port numbering system has three tiers:
- Well-known ports (0–1023): Reserved for fundamental protocols — HTTP, HTTPS, SSH, DNS. Binding these requires elevated privileges.
- Registered ports (1024–49151): Where vendors like Oracle register their software's ports with IANA. No privilege required to bind, but orderly registration prevents conflicts.
- Dynamic/ephemeral ports (49152–65535): Used temporarily by operating systems for outgoing connections. Unregistered and untracked.
The registered range is where most enterprise software lives. When Oracle needed a port for Enterprise Manager's cloud gateway, they applied to IANA, got 1748 assigned, and built their software around it. The alternative — software randomly choosing ports — would make firewall configuration a nightmare.
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