#### io_context::run_one

Run the `io_context` object's event processing loop to execute at most one handler.

    count_type run_one();

The `run_one()` function blocks until one handler has been dispatched, or until the `io_context` has been stopped.

###### Return Value

The number of handlers that were executed. A zero return value implies that the `io_context` object is stopped (the `stopped()` function returns `true`). Subsequent calls to `run()`, `run_one()`, `poll()` or `poll_one()` will return immediately unless there is a prior call to `restart()`.

###### Remarks

Calling the `run_one()` function from a thread that is currently calling one of `run()`, `run_one()`, `run_for()`, `run_until()`, `poll()` or `poll_one()` on the same `io_context` object may introduce the potential for deadlock. It is the caller's responsibility to avoid this.