Serial Tester¶
Summary¶
Serial Tester (SerialTester.exe) is a free Windows utility — originally developed and distributed by MRMC — for monitoring and diagnosing UDP, FreeD, OSC, and serial data streams. It is the standard first-step diagnostic tool whenever Flair's real-time data output is not reaching Unreal Engine, Disguise, Aximmetry, a lighting desk, or any other receiver application.
The tool runs without installation (portable .exe). You run it on the receiving machine, point it at the correct UDP port, click Listen, and it shows you exactly what data is arriving — or confirms that nothing is arriving at all. That single test splits every data output problem into two categories: Flair is or is not sending, and the problem is on the sending side or the receiving side.
Downloads:
| Version | Size | Notes |
|---|---|---|
| Serial-Tester.exe | 793 KB | Current — includes FreeD, OSC, and UDP tabs (2024 update by Simon Wakley) |
| Serial-Tester-v2.exe | 793 KB | Same as above — explicit v2 filename |
| Serial-Tester-v1.exe | 19 KB | Original v1.3 (2013) — serial/UDP only, no FreeD or OSC tabs |
Windows only — no install required
SerialTester.exe is a portable Windows executable. No installer, no admin rights needed. Just download and run. Use the current version unless you specifically need legacy v1.3 serial-only behaviour.
What It Does¶
Serial Tester receives and displays live data on several protocol tabs:
| Tab / Mode | Use |
|---|---|
| FreeD | Verify Flair is sending FreeD camera tracking data (XYZ position, pan/tilt/roll, focus, zoom). Standard for Unreal Engine / Disguise / Aximmetry LiveLink setup |
| OSC | Monitor incoming OSC messages from Flair's OSC XYZ output, or test OSC commands being sent to Flair |
| UDP | Raw UDP packet monitoring for custom or less common protocols |
| Serial | RS-232 / serial port monitoring (legacy cameras, VTRs, lens motors, third-party devices connected via COM port) |
Each tab shows live incoming packet data as the robot moves, giving you a real-time view of what Flair is actually sending on the network.
Why It's the First Diagnostic Step¶
When Unreal Engine (or any other VP app) shows no data from Flair, the problem could be in:
- Flair's Serial Devices Setup (wrong IP, wrong port, wrong protocol, data output not enabled)
- The network path between Flair PC and receiver PC (subnet mismatch, wrong NIC, InTime network vs Windows network)
- Windows Firewall on either machine blocking the UDP port
- The receiver application itself (incorrect port, incorrect IP, plugin not configured)
Serial Tester lets you verify the first three independently of the receiver app, before you spend time troubleshooting Unreal or Disguise.
The standard diagnostic workflow:
- Close the receiver application (Unreal, Disguise, etc.).
- Run Serial Tester on the receiving machine.
- Set the port to match Flair's configured output port (FreeD default: 5900; OSC default: 55535).
- Click Open UDP (FreeD mode) or Listen (OSC mode).
- Move the robot in Flair.
- If Serial Tester shows data — Flair is sending correctly. The problem is in the receiver app.
- If Serial Tester shows nothing — the problem is in Flair's output setup or the network path.
Critical: Serial Tester Holds the Port¶
Only one app can bind a UDP port at a time
Serial Tester takes exclusive ownership of the UDP port it listens on. If Serial Tester is open and listening on port 55535, Unreal Engine cannot receive on that port simultaneously — it is already bound. Always close Serial Tester completely before testing whether the actual receiver application is working.
Multiple operators have lost time troubleshooting Unreal when the real problem was that Serial Tester was left running in the background.
Network Setup for FreeD / OSC Output¶
Most Flair PCs use InTime, and the real-time data output does not leave via the Windows network adapter — it goes out via the dedicated Network Direct port connected to the RT-12/14 switch in the Flair flight case.
The receiving machine (running Serial Tester or Unreal) must be:
- Connected to the same RT-12/14 switch or on the same physical network segment.
- Assigned a static IP address on the 192.168.1.xxx subnet.
- Not using the same IP as the Flair PC (default: 192.168.1.10) or any other device on the network.
- Subnet mask: 255.255.255.0 — gateway: blank.
This is configured in Flair under Setups → Serial Devices Setup → Data Output.
For FreeD output, set the port to 5900 in Flair and match it in Serial Tester.
How to Use Serial Tester¶
FreeD verification (Unreal Engine / Disguise setup)¶
- In Flair, go to Setups → Serial Devices Setup → Data Output.
- Select FreeD format, enable UDP, and enter the IP of the receiving machine.
- Set the port to 5900 (or your configured port).
- Apply and save, then exit the dialog.
- On the receiving machine, run SerialTester.exe.
- Select the Free D tab.
- Set the port to 5900 and click Open UDP.
- Move or jog the robot in Flair — camera XYZ and rotation data should appear immediately.
OSC verification¶
- In Flair, configure Setups → Serial Devices Setup → Data Output to OSC XYZ, UDP, target IP, port 55535.
- On the receiving machine, run SerialTester.exe.
- Select the OSC tab, set port to 55535, click Listen.
- Jog the robot in Flair — OSC packets (e.g.
\Flair\Track,\Flair\Angle) appear in real time.
Common Issues¶
Serial Tester shows nothing at all:
- Confirm the receiving machine is on the 192.168.1.xxx subnet (not a different network).
- Confirm the InTime/RT switch is connected — FreeD data does not leave via the standard Windows NIC on an InTime system.
- Check Windows Firewall on both machines — Windows may block the UDP port, or show a silent pop-up asking "Allow this app on public / private network?" that was dismissed without clicking Allow.
- Confirm Flair's output is pointing to the correct IP of the receiving machine (not 127.0.0.1 or a wrong address).
Serial Tester shows data but Unreal shows nothing:
- Serial Tester is holding the port. Close Serial Tester, then retest in Unreal.
- On some systems, rebooting the receiving machine after closing Serial Tester is required before Unreal can bind the port cleanly. This is a known quirk reported by multiple operators.
Serial Tester sees data but values look wrong:
- Confirm the FreeD tab is selected (not OSC or UDP raw) if testing FreeD output.
- Confirm Flair's Transform Export is set correctly: Focus Export = Millimetres, Zoom = mm × 1000.
- The old FreeD data format (50 Hz XYZ) shows focus values as raw fractions (e.g. 0.085 for 300 cm). The OSC XYZ format shows focus in metres (3.000 for 300 cm). Both are valid — you need to match the format to your receiver's expectations.
Version History¶
The original Serial Tester (v1.3, 2013) was a basic serial/UDP listener. An updated version including OSC and FreeD tabs was shared by Simon Wakley (MRMC, Flair developer) via the community chat in July 2024. The download link above points to this updated version.
"What's the best place to find the latest version of serial tester? The one on the downloads page is version 1.3 from 2013." — David Jeffries, community chat, 20 July 2024
"Has OSC and other things, not sure when these were added, but this is the latest." — Simon Wakley, community chat, 20 July 2024
Evidence¶
"It comes up from time to time that some have trouble with the real-time data output from Flair. It is pretty thoroughly tested and works for many people so if you can't see anything on the receiving computer or on the Serial Tester software then most likely you're not connected right." — Gordon Eschke (MRMC Admin), Talk.MrMoco forum, April 2021
"You can see it using the Serial Data tester - Do you have that? SerialTester.exe" — Simon Wakley (Flair developer), community chat, September 2024
"Serial Tester is up and working fine, FreeD data coming in." — Heiko Matting, community chat, September 2024
"I had an issue once where I had a pop-window for the serial tester to allow it access to network, and didn't see it and didn't click 'allow'." — Riley Morgan, community chat, February 2023
"Weirdly when i use serial tester i have to reboot my pc before i can see in unreal." — Stafford Wheaton, community chat, May 2025
"And that you've closed serial tester or anything else that may have been using that port." — David Jeffries, community chat, June 2025
"1. On the Unreal workstation, download the serial tester app from our website. 2. Close Unreal Engine if running. 3. Run the SerialTester app. 4. Set the port number to 5900 (matching their configuration), then click 'Open UDP'. 5. Click the 'Free D' tab. The data from Flair should be shown. You should verify there are sensible values in the X, Y and Z camera position." — MRMC Support, community chat, October 2025
Download¶
| File | Link |
|---|---|
| Serial-Tester.exe (latest, includes FreeD + OSC) | Download |
Windows only. No installation required — run the .exe directly.
The original MRMC download server link (mrmoco.com/download/30041/) is no longer reliable following MRMC's liquidation in 2026. Use the link above.
Related Pages¶
- Serial Tester — Detailed Diagnostics Issue Page
- Serial Device Did Not Send Bytes
- Reserved IP Addresses and Conflicts