open
suspend fun open(uri: String, client: HttpClient? = null, headers: Map<String, String> = emptyMap(), policy: HttpReaderPolicy = HttpReaderPolicy()): KtorMediaIo
Probes uri and returns a reader positioned at byte zero. The probe's own response body becomes the first stream, so a plain open costs exactly one request.
A null client creates a private one from the platform engine on the classpath and closes it with the reader; a shared client stays the caller's to close. policy limits every wait, this probe's included.