Watch devices

Google ADB Server can also notify clients when devices are connected or disconnected. So you don't need to poll the server to get the latest device list.

declare class AdbServerClient {
  trackDevices(
    signal?: AbortSignal
  ): AsyncGenerator<AdbServerClient.Device[], void, void>;
}

The returned generator will yield the updated device list when it's changed. By using an async generator instead of a callback, it can throw errors when something goes wrong.

for await (const devices of client.trackDevices()) {
  console.log(devices);
}

signal

An AbortSignal object can be passed to stop watching devices.

const controller = new AbortController();
setTimeout(() => controller.abort(), 10000);

for await (const devices of client.trackDevices(controller.signal)) {
  console.log(devices);
}

Note that unlike many other AbortSignal consumers, trackDevices will return normally when the signal is aborted, instead of throwing signal.reason.

Find changed devices

Although the generator yields the current device list, it doesn't directly tell you which device is connected or disconnected. You need to diff the device list yourself.

let lastDevices: AdbServerClient.Device[] = [];
for await (const devices of client.trackDevices()) {
  const connected = devices.filter(
    (device) =>
      !lastDevices.some((last) => last.transportId === device.transportId)
  );
  const disconnected = lastDevices.filter(
    (last) => !devices.some((device) => device.transportId === last.transportId)
  );

  console.log("Connected:", connected);
  console.log("Disconnected:", disconnected);

  lastDevices = devices;
}