sendTo

Send to one peer. Suspends until accepted by the local transport.

A send failure must NOT be reported as a cancellation

Throw an ordinary exception when the frame cannot be handed to the transport. An implementation must not let a CancellationException out of this method (or out of broadcast) unless it is signalling the caller's own cancellation, because the caller cannot tell the two apart: the idiomatic guard (runCatchingCancellable) rethrows any CancellationException, and a rethrown one cancels the calling coroutine rather than failing it — no failure handler runs, and there is not even a stack trace to find it by.

The trap is withTimeout(sendTimeout) { … }. withTimeout throws TimeoutCancellationException — which is a CancellationException — to its caller, without cancelling that caller's job. Convert it before it escapes: withTimeoutOrNull plus an explicit throw, or catch it and rethrow as a plain Exception.

This is the same obligation Loom.weave carries, for the same reason, and it is stated on both because a contract only one method carries is what let a real bug through: a long-lived consumer loop that sends per recipient is cancelled — not failed — by one such throw, so it stops sending for the rest of the session in complete silence. A caller that cannot afford to trust this should guard with try/catch plus currentCoroutineContext().ensureActive() rather than runCatchingCancellable; CompositeSeam.reconcile and SeamRoom's admit fan-out writer are the in-tree patterns.

Throws