getVersion

declare class AdbServerClient {
  getVersion(): Promise<number>;
}

The protocol between ADB client and server has its own version number. This is not Android version (like 13.0), nor ADB protocol version (like 0x10000001), nor platform tools version (like 34.0.1).

This is the version you see in the error message when you use a wrong ADB client to connect to a server:

adb server version (39) doesn't match this client (41); killing...

Some features (for example waitFor) requires a certain version to work.

Equivalent ADB Command

adb version

If it prints Android Debug Bridge version 1.0.41, the protocol version is 41.