stream_drd() discarded the pooled connection and forced a fresh connect.
The NL43 allows only one TCP connection at a time; over a cellular link
the device does not free its single slot fast enough for an immediate
reconnect, so the fresh connect times out — the live DRD stream fails
while start/stop commands (which reuse the warm pooled socket) keep
working. This surfaced once the persistent connection pool was enabled
(TCP_PERSISTENT_ENABLED=true).
Stream over the already-open pooled connection via acquire() instead of
discard()+_open_connection(), and release() it back to the pool on exit
(after sending SUB to stop the stream) so commands keep reusing the same
single socket. The per-device lock is held for the whole streaming
session, so the poller can't touch the socket concurrently.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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