StreamHub — User Guide

StreamHub turns signals streamed by MARTe2 UDPStreamer DataSources into a multi-user oscilloscope. One hub process aggregates any number of sources and serves up to 16 simultaneous clients: a browser SPA and/or the native ImGui desktop client.

MARTe2 app (UDPStreamer) ──UDP 44500──▶ StreamHub ──WebSocket 8090──▶ browser / ImGui

1. Quick start (demo stack)

source env.sh
./run_streamhub.sh -w -g

This builds everything, starts a demo MARTe2 application with three streamers (scalars over multicast, two array streamers), a StreamHub on port 8090, the web UI server on port 8080 (-w) and the ImGui client (-g). Then open:

http://localhost:8080/?hub=localhost:8090

Useful flags: -p <port> WS port, -n <pts> ring size, -s skip rebuild, -h full help (including the list of ports used).

2. Running against your own application

Add a UDPStreamer DataSource to your MARTe2 configuration (see UDPStreamer.md).
Write a hub configuration, e.g. hub.cfg:
```
WSPort   = 8090
Sources = {
    MyApp = { Label = "MyApp" Addr = "192.168.0.10" Port = 44500 }
}
```
For multicast streamers add MulticastGroup = "239.0.0.1" and DataPort = 44503. All keys and defaults: StreamHub-Developer.md §6.

Run the hub and a client:

source env.sh
./Build/x86-linux/StreamHub/StreamHub.ex -cfg hub.cfg

# web UI
cd Client/webui && go build -o streamhub-webui . && ./streamhub-webui
# then browse http://localhost:8080/?hub=<hub-host>:8090

# or native client
./Client/streamhub/build/StreamHubClient -host <hub-host> -port 8090

Sources can also be added at runtime from either client ("Add source": label + host:port, optional multicast group/data port). "Save sources" persists the runtime list to streamhub_sources.json so the hub reloads it on restart.

3. Using the oscilloscope (web UI and ImGui)

Both clients offer the same workflow:

Plotting — drag signals from the source sidebar onto a plot. Choose a grid layout (1×1 … 4×1 / 2×2 / 1×4). Live plots scroll with wall-clock time; pick the time window (1/5/10/30/60 s).
Zoom — scroll/drag to zoom. When zoomed in, the client automatically fetches high-resolution data from the hub for the visible window. Back steps through the zoom history, Fit frames the data, Reset/Live returns to the scrolling live view.
Cursors — enable cursors A/B and drag them; the readout shows ΔT and the value of each trace at both cursors.
V-scale modes — normal, digital (booleans stacked as logic traces), mixed.
Signal styling — per-trace colour, line width, markers.
Stats — per source: packet rate ± std, lost packets, fragments and bytes per cycle, cycle-time min/avg/max/std and a 20-bin cycle-time histogram.

4. Trigger

The trigger runs in the hub, so a capture is identical in every connected client and uses full-rate ring data (not the decimated live stream).

Pick the trigger signal (for array signals: a specific element), the edge (rising/falling/both) and the threshold.
Pick the capture window (100 µs … 10 s) and the pre-trigger percentage (how much of the window precedes the trigger instant).
Mode normal re-arms automatically ~200 ms after each capture (Stop pauses re-arming); mode single captures once and waits for Rearm.
Press Arm. Badge states: IDLE → ARMED → COLLECTING → TRIGGERED.

On capture, the trigger view shows all plotted signals relative to the trigger instant (marker at t = 0) over [-pre, +post].

5. Troubleshooting

Symptom	Check
Source stuck in connecting	Streamer host/port reachable? For multicast: group/data port match the streamer, and routing allows IGMP
No data but source streaming	`getStats` rate ≈ RT cycle rate? Firewall on UDP data port?
Web UI loads but no signals	Did you pass `?hub=host:8090` (the SPA talks WS directly to the hub, not the web server)?
Trigger never fires	Threshold inside the signal's actual range? Edge direction correct?
Time axis jumps once at start	Normal: first-packet wall-clock calibration; it also re-anchors after a source restart

Hub-side logs go to stdout; the demo scripts write /tmp/streamhub_e2e_{marte,hub}.log.

6. Further reading

StreamHub-API.md — WebSocket protocol (write your own client)
StreamHub-Developer.md — internals, build, tests
UDPStreamer.md — configuring the MARTe2 DataSource
Protocol.md — UDPS wire format

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