Service: PREDICT (satellite tracking)
Protocol: UDP
Port range: Registered (1024-49151)
Status: Officially assigned by IANA
What This Port Does
Port 1210 carries satellite tracking data from PREDICT, a satellite tracking and orbital prediction program. When you want to know where a satellite is right now, or when it will pass overhead, or what direction to point your antenna—PREDICT on port 1210 provides those answers.1
The protocol is simple: clients connect via UDP to a PREDICT server running on port 1210, request tracking data for specific satellites, and receive real-time position, velocity, elevation, azimuth, and pass prediction information.
Who Uses This
Amateur radio operators. Ham radio enthusiasts who communicate through satellites, receive weather satellite images, or track the International Space Station. PREDICT tells them when satellites will be visible from their location—when to turn on their equipment and where to point their antennas.2
The software tracks up to 24 satellites simultaneously. Clients can query any satellite in the database and get live tracking data as long as they're connected to a PREDICT server on the network.
The History
PREDICT was written by John A. Magliacane (KD2BD) for Linux systems. It's open-source software that became the standard satellite tracking tool for amateur radio operators who needed accurate orbital predictions without expensive commercial software.3
The program calculates satellite positions using orbital mechanics and Two-Line Element (TLE) data—the standard format for describing satellite orbits. Port 1210 became the conventional port for PREDICT's network interface, allowing the program to operate as a server for multiple client applications.
How It Works
PREDICT runs in server mode, continuously tracking satellites and making that data available over the network. Clients connect to port 1210/UDP and send requests for specific satellites. The server responds with:
- Current position (latitude, longitude, altitude)
- Velocity and direction
- Elevation and azimuth from the observer's location
- Range and range rate
- Next pass predictions (rise time, set time, maximum elevation)
The UDP protocol makes sense here—tracking data needs to be fast and near-real-time. A dropped packet just means you request fresh data. The satellite's position is constantly changing anyway.
The Range This Port Belongs To
Port 1210 sits in the registered port range (1024-49151). These ports are registered with IANA for specific services, but the registration is less strict than well-known ports. Anyone can use them, but they're documented to reduce conflicts.
Registered ports cover the middle ground—services that are real and established but not fundamental Internet infrastructure. PREDICT fits perfectly here: it's a legitimate service with a defined protocol, but it's not something every computer needs.
Why This Port Matters
Amateur radio satellite communication depends on precise timing. Satellites move fast—orbiting Earth every 90 minutes or so. The window to communicate might be 10 minutes. Miss it, and you wait hours for the next pass.
PREDICT on port 1210 solves the coordination problem. Instead of every operator running tracking software locally, a single PREDICT server can provide data to multiple clients, radios, antenna rotators—anything that needs to know where satellites are.
It's infrastructure for a specific community, but that community depends on it.
Security Considerations
PREDICT on port 1210 typically runs on private networks or trusted local environments. The protocol has no built-in authentication or encryption—it was designed for amateur radio operators who trust each other and often operate on local networks.
If you're running a PREDICT server accessible from the Internet, understand that anyone can query it for satellite tracking data. The data itself isn't sensitive—satellite positions are public information—but you may not want to advertise what you're tracking or when you're operating.
Firewall rules should restrict port 1210 to trusted networks unless you specifically intend to provide public tracking data.
Checking What's on Port 1210
To see if PREDICT or anything else is listening on port 1210:
Linux/Mac:
Windows:
If nothing appears, the port is unused. If you see a process, check what's running—it should be PREDICT if you're running satellite tracking software, or possibly something else using the port unofficially.
Related Ports
Other amateur radio and satellite-related services scatter across the port range, often in the registered or dynamic ranges:
- Port 4533 - Hamlib (amateur radio control libraries)
- Port 7355 - Gpredict (another satellite tracking program)
- Various amateur radio digital modes use different ports
Each amateur radio application picked a port that wasn't already taken, creating a loose constellation of services that the ham radio community knows about but that don't appear in mainstream documentation.
Frequently Asked Questions About Port 1210
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