##### io_service::run (1 of 2 overloads)

Run the io_service's event processing loop.

    std::size_t run();

The run() function blocks until all work has finished and there are no more handlers to be dispatched, or until the io_service has been stopped.

Multiple threads may call the run() function to set up a pool of threads from which the io_service may execute handlers. All threads that are waiting in the pool are equivalent and the io_service may choose any one of them to invoke a handler.

The run() function may be safely called again once it has completed only after a call to reset().

###### Return Value

The number of handlers that were executed.

###### Exceptions

asio::system_error

  Thrown on failure.

###### Remarks

The poll() function may also be used to dispatch ready handlers, but without blocking.