TCI Server Overview¶

The TCI Server applet runs a WebSocket server that speaks the Expert Electronics TCI protocol, letting third-party logging, digital-mode, and SDR applications — such as Log4OM and SunSDR tools — read and control the radio over a local network connection. Open the applet to start the server, set the port, and adjust audio gain for each RX and TX channel.

TCI TX audio is received over the WebSocket and fed into a dedicated dax_tx stream slot that is independent of the Windows SmartSDR DAX2 audio device path, so TCI TX works on all platforms including Windows and Linux without PipeWire (v0.9.5.1).
A crash-on-quit was fixed in v0.9.7: TciServer is now explicitly torn down in ~MainWindow() after the audio thread stops but while RadioModel is still alive, preventing a use-after-free via releaseDaxForTci(). A belt-and-braces QPointer<RadioModel> was added so existing null-guards catch any future regression automatically.
Three TCI v2.0 commands (volume, drive, rx_volume) were added to the dispatch table with bidirectional state sync in v26.5.1.
Panadapter spectrum forwarding and tx_gain / ALC were added in v26.5.3.
Right-click the TX slider to pick TX overflow handling (Clip / NaNGuard / Measure) for bit-exact digital-mode tone fidelity.

Before you start¶

AetherSDR must be connected to the radio. The TCI applet requires an active radio connection.
This feature is only present in builds compiled with WebSocket support (HAVE_WEBSOCKETS). If the TCI tray button is absent, your build does not include TCI.

How it works¶

The TCI applet is hidden by default. Toggle it open with the TCI tray button on the right sidebar.

When you click Enable, AetherSDR binds a WebSocket server on the configured port (default 50001). Any TCI-compatible client that connects to ws://<your-host>:<port> can then query and command the radio using the TCI protocol. The applet displays the current server state and connected client count in the status area next to the Enable button.

RX audio for channels 1–4 follows the same DAX channel assignments as the DAX applet. The slice letter shown beside each RX and TX row — for example, Slice A — reflects whichever slice is currently assigned to that DAX channel. If no slice is assigned, the indicator shows —.

Gain levels set in the applet apply to the TCI audio stream and are independent of the radio's RF gain controls.

What each control does¶

Control	What it does	Default
RX1–RX4 gain+meter	Combined level meter and gain slider for each TCI RX channel. Drag to set the output gain for that channel's audio stream. The slider has an accessible name set to "TCI RX N gain".	0.5
TX gain+meter	Combined level meter and gain slider for TCI TX gain. Drag to set the output gain for the TX audio stream. The slider has an accessible name set to "TCI TX gain". Right-click opens TX overflow-mode picker (Clip / NaNGuard / Measure).	TciServer::setTxGain persists TciTxGain internally; UI mirrors the stored value. TCI TX audio is always allowed regardless of platform or hosted-DAX availability (evaluateDaxTxPolicy now unconditionally allows DaxTxRequestReason::TciTxAudio, v0.9.5.1, #2276). Right-click menu lets users choose how out-of-range (>1.0) samples from digital-mode clients are handled: Clip (saturating ±1.0, legacy default), NaNGuard (pass-through, only zero NaN/Inf), or Measure (true bypass with clip counting). Default is Clip so existing users see no behavior change (#3065).
RX/TX slice-assignment labels	Read-only indicators showing which slice drives each row (`Slice A`, `Slice B`, etc., or `—` if unassigned). Uses rich text formatting so slice letters render correctly (#2606).	`—`
Port	WebSocket port the server listens on. Changing the value while the server is running restarts it on the new port. Values outside the valid range snap back to `50001`.	`50001`
Enable	Starts or stops the TCI server. If the port is already in use, the button snaps back to off and the status shows `(port in use)`.	Off
Server status	Displays `(stopped)`, `:<port> (<N> clients)`, or `(port in use)`. Turns red on a bind failure.	`(stopped)`
TX overflow mode (right-click)	Right-click the TX gain meter/slider to open a context menu selecting the TX overflow handling mode. Emits tciTxOverflowModeChanged.	Clip. Clip clamps overshoots to ±1.0 with harmonic distortion; NaNGuard preserves bit-exact digital tones by only zeroing NaN/Inf; Measure counts overshoots for telemetry without mutation. Persisted as `TciTxOverflowMode` (0/½).

TX overflow mode details¶

Right-click the TX gain+meter control to open a context menu with three options:

Mode	Behavior
Clip (0)	Hard-clamp overshoots to ±1.0. Defensive default; introduces harmonics on overshoot but protects downstream int16 conversion.
NaNGuard (1)	Pass samples through bit-exact; only zero pathological NaN/Inf values. Preserves digital-mode tone fidelity; out-of-range floats reach the radio.
Measure (2)	Never mutate samples. Count overshoots for telemetry; the downstream int16 conversion still clamps in the radio-native DAX route.

The setting is persisted as TciTxOverflowMode and defaults to 0 (Clip) so existing users see no behavior change.

Tips¶

To start the TCI server automatically every time AetherSDR launches, enable Settings > Autostart TCI with AetherSDR. This sets the AutoStartTCI preference.
The client count shown in the server status updates live as clients connect and disconnect. See See how many TCI clients are connected for details.

Troubleshooting¶

Status shows (port in use) and Enable snaps off — Another process is already bound to that port. Change the port in the Port field to a free port in the range 1024–65535 and click Enable again. See Change the TCI port.
TCI tray button is missing — This build of AetherSDR was compiled without WebSocket support. TCI is unavailable.
Slice labels show — for all channels — No slices have a DAX channel assigned. Assign a DAX channel to a slice through the radio setup to populate the RX and TX labels.