* We must not close the socket manually (with `client_socket.close`), as this would close it twice. Compare: 2c83794b85/lib/tubesock.rb (L92)
* When the socket is closed twice, nginx registers a `Connection reset by peer` error: `recv() failed (104: Connection reset by peer) while proxying upgraded connection`
* Tubesock automatically closes the socket when the `hijack` block ends and otherwise ignores `Errno::ECONNRESET`: 2c83794b85/lib/tubesock.rb (L161-L162)
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