Change the base TCP port¶

The CAT Control applet runs up to four rigctld-compatible TCP servers on consecutive ports starting from a configurable base. Change the base port when the default conflicts with another application on your system.

Before you start¶

AetherSDR must be connected to the radio. The CAT applet requires an active radio connection.
Open the CAT Control applet by clicking the CAT tray button on the right sidebar if it is not already visible.

Steps¶

In the CAT Control applet, locate the Base: label and its text field at the bottom of the applet.
Click the Base: field and type the new port number. Valid range: 1024–65535. Default: 4532.
Press Enter or Tab to confirm. If the value is outside the valid range, it snaps back to 4532.
The new base port is saved immediately to CatTcpPort.
If Enable TCP is currently active, all four servers restart automatically on the new ports (base, base+1, base+2, base+3). No further action is needed.

What each control does¶

Control	Kind	Default
`Base:`	Text field	`4532`
`Enable CAT`	Toggle button	Disabled
Enable checkboxes	Checkbox	Unchecked
A/B/C/D channel rows	Indicator	`(stopped)`

The main toggle button shows Enabled when CAT servers are active and Disabled when they are off. The same label appears in both the docked and floating applet views.

Each channel row includes a per-channel enable checkbox. The checkbox has a high-contrast border and fills with an accent color when checked, making the on/off state readable at a glance against the dark applet background.

Tips¶

Choose a base port that leaves the next three consecutive ports free. For example, a base of 4532 uses 4532, 4533, 4534, and 4535.
If you change the port while Enable CAT is off, the servers will start on the new port the next time you click Enable CAT.
On Linux and macOS, each channel exposes a PTY symlink when the corresponding enable checkbox is checked. Point your logging software to the symlink path displayed below each channel label.
In v26.5.3, PTY symlinks are created per-user under $XDG_RUNTIME_DIR/aethersdr/cat-A through cat-D on Linux, or ~/Library/Caches/AetherSDR/cat-A through cat-D on macOS. This change from the previous /tmp/AetherSDR-CAT-* location fixes a security vulnerability (GHSA-qxhr-cwrc-pvrm) and uses atomic symlink replacement to prevent time-of-check/time-of-use (TOCTOU) race conditions.

Troubleshooting¶

Servers do not restart after changing the port — Confirm you pressed Enter or Tab to finish editing the Base: field. Clicking away without committing the edit may not apply the change.
Port field snaps back to 4532 — The value entered was outside the 1024–65535 range. Enter a value within that range.
Server fails to start on the new port — Another application may already be using that port or one of the three consecutive ports. Choose a different base port.
PTY symlinks do not appear — Enable TTY is available on Linux and macOS only. Confirm you checked the enable checkbox for that channel and that AetherSDR has write access to the per-user runtime directory. On Linux this is typically $XDG_RUNTIME_DIR/aethersdr/; on macOS ~/Library/Caches/AetherSDR/.