Calling accept() from multiple threads
As mentioned in the StackOverflow answer you linked, a single thread calling accept() is probably the way to go. You mention concerns about locking, but these days you will find lockfree queue implementations available in Boost.Lockfree, Intel TBB, and elsewhere. You could use one of those if you like, but you might just use a condition variable to let your worker threads sleep and wake one of them when a new connection is established.