A dependency-free Java library and the camera-control command-line client for Camera Control protocol version 4. It supports status, idempotent single capture, and cancellable time-lapse operation over verified TLS. Status polling reconnects with bounded exponential backoff when Wi-Fi or the server connection is interrupted.

The client uses java.net.http.WebSocket and a small bundled JSON reader, so the shipped JAR has no runtime dependencies at all.

• JDK 17 or newer
• Camera Control's TLS-only WebSocket API enabled and running
• The verified local CA certificate shown by the phone app

cd java
mvn package

The build produces target/camera-control-client-0.1.0.jar with an executable manifest. Set the password without exposing it in process arguments:

export CAMERA_CONTROL_PASSWORD='your password'

If this variable isn't present, the CLI prompts on the console without echoing the password.

Read camera, device, capture-session, and reliability status:

java -jar target/camera-control-client-0.1.0.jar \
  status wss://192.168.1.50:8080/ws \
  --ca camera-control-local-ca.crt

Capture and save one JPEG through the idempotent job API:

java -jar target/camera-control-client-0.1.0.jar \
  capture wss://192.168.1.50:8080/ws \
  --ca camera-control-local-ca.crt \
  --camera 1 --resolution high --flash off \
  --jpeg-quality 90 --rotation 90 --output photo.jpg

Rotation accepts 0, 90, 180, or 270 clockwise degrees. Omit the flag to keep the current app setting; use --rotation 0 to reset it. The app starts at 0°. Rotation applies to new photos and live previews; existing gallery photos keep their orientation. Library callers pass "rotation": 90 in the existing controls map. Check status.capabilities.rotation for support.

Start a 5-second time lapse, stopping after 20 photos:

java -jar target/camera-control-client-0.1.0.jar \
  time-lapse wss://192.168.1.50:8080/ws \
  --ca camera-control-local-ca.crt \
  --interval 5 --count 20

Omit --count to run until Ctrl+C, or use --duration SECONDS.

import app.flutterdev.cameracontrol.CameraControlClient;
import app.flutterdev.cameracontrol.CameraControlClient.CaptureOptions;
import app.flutterdev.cameracontrol.CameraControlClient.Options;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Map;

try (CameraControlClient camera = CameraControlClient.withCaFile(
    "wss://192.168.1.50:8080/ws",
    System.getenv("CAMERA_CONTROL_PASSWORD"),
    Path.of("camera-control-local-ca.crt"),
    Options.defaults())) {

  camera.connect();
  System.out.println(camera.status());

  Map<String, Object> job = camera.captureJob(
      CaptureOptions.defaults().withRequestId("document-page-42"));
  Map<String, Object> result =
      CameraControlClient.objectField(job, "result", "job.result");
  Files.write(Path.of("photo.jpg"), CameraControlClient.decodePhoto(
      CameraControlClient.objectField(result, "photo", "job.result.photo")));
}

captureJob retries reuse the same semantic requestId, allowing the running app process to deduplicate an ambiguous reconnect. Do not deliberately reuse a request ID with different capture settings. If the phone app itself restarts, its in-memory idempotency history is lost; verify status before replaying an ambiguous capture.

A CameraControlClient is not safe for concurrent use by multiple threads.

Download the CA from the URL shown by the app, then compare its SHA-256 fingerprint with the phone before trusting it:

curl --insecure --output camera-control-local-ca.crt \
  https://192.168.1.50:8080/ca.crt
openssl x509 -in camera-control-local-ca.crt -noout -fingerprint -sha256

--insecure is only for the initial CA download. WebSocketChannel builds a KeyStore containing only this certificate and an SSLContext that trusts nothing else.

Run tests with:

mvn test

See ../api.md for the command and event summary.