And yet, one thought that keeps banging against my head is this:   “even if we can ‘make it to work,” does it ‘make sense?’”   That, to me, is actually a key question here:   “does it actually ‘make sense’ that one thread should ‘only read,’ and that another thread, ‘only write?’”   I don’t think so.   Why?   Because somebody needs to be aware of:   “the present-state of the remote client.”   And, furthermore, this “present-state” can only be ascertained, subject to an unforeseen (and, unforeseeable ...) lag.

Therefore, I suggest that the only truly-practicable design must be this:   “put your letter in the box, raise the flag, and then wait for the postman.”   “The Postman” has no race-conditions within himself.   Therefore, he is able to efficiently serve the needs of any number of clients without conflict.

To my way of thinking, both of the client-processes in question should be reading/writing from queues that are served by the Postman.   They should not be attempting to read/write from the socket directly.