Google Cast closes a control connection that goes roughly 10 seconds without a heartbeat PING. QBZ pinged every 25 seconds, so any cast connection left idle between connect and load — for example while the track downloads, or across a delayed second play attempt — was dropped by the receiver. The next LOAD then failed with EPIPE (broken pipe): the device chimed on connect but never played audio, and the heartbeat thread logged repeating broken-pipe warnings.
Pinging every 5s is the cadence the Cast protocol expects and keeps the connection alive through those idle gaps.
Fixes#439.
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vicrodh
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