* Exactly 1 sending thread per an RPC connection.
* If the calling thread is interrupted before the socket write, it will be skipped instead of sending it anyways.
* If the calling thread is interrupted during the socket write, the write will finish.
* RPC requests will be written to the socket in the order received.
* Sending thread is only started by the receiving thread.
* The sending thread periodically checks the shouldCloseConnection flag.
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