A library notification connection that timed out could still complete later and stay open after the owner was disposed. IOWebSocketChannel.connect applies connectTimeout with Future.timeout and drops the pending connect, so nothing could ever close a socket that finished late.
The channel factory now resolves only to established channels: it owns WebSocket.connect, applies its own deadline, closes a late upgrade, and returns a channel built from the resolved socket. The socket class no longer holds half-open channels, which also removes the connected-flag workaround around the library's close semantics.
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