io_service

Provides core I/O functionality.

class io_service :
  noncopyable

Types

Name	Description
id	Class used to uniquely identify a service.
service	Base class for all io_service services.
strand	Provides serialised handler execution.
work	Class to inform the io_service when it has work to do.

Member Functions

Name	Description
dispatch	Request the io_service to invoke the given handler.
io_service	Constructor.
poll	Run the io_service's event processing loop to execute ready handlers.
poll_one	Run the io_service's event processing loop to execute one ready handler.
post	Request the io_service to invoke the given handler and return immediately.
reset	Reset the io_service in preparation for a subsequent run() invocation.
run	Run the io_service's event processing loop.
run_one	Run the io_service's event processing loop to execute at most one handler.
stop	Stop the io_service's event processing loop.
wrap	Create a new handler that automatically dispatches the wrapped handler on the io_service.
~io_service	Destructor.

Friends

Name	Description
add_service	Add a service object to the io_service.
has_service	Determine if an io_service contains a specified service type.
use_service	Obtain the service object corresponding to the given type.

The io_service class provides the core I/O functionality for users of the asynchronous I/O objects, including:

boost::asio::ip::tcp::socket
boost::asio::ip::tcp::acceptor
boost::asio::ip::udp::socket
boost::asio::deadline_timer.

The io_service class also includes facilities intended for developers of custom asynchronous services.

Thread Safety

Distinct objects: Safe.

Shared objects: Safe, with the exception that calling reset() while there are unfinished run() calls results in undefined behaviour.

Effect of exceptions thrown from handlers

If an exception is thrown from a handler, the exception is allowed to propagate through the throwing thread's invocation of boost::asio::io_service::run(), boost::asio::io_service::run_one(), boost::asio::io_service::poll() or boost::asio::io_service::poll_one(). No other threads that are calling any of these functions are affected. It is then the responsibility of the application to catch the exception.

After the exception has been caught, the boost::asio::io_service::run(), boost::asio::io_service::run_one(), boost::asio::io_service::poll() or boost::asio::io_service::poll_one() call may be restarted without the need for an intervening call to boost::asio::io_service::reset(). This allows the thread to rejoin the io_service's thread pool without impacting any other threads in the pool.

For example:

boost::asio::io_service io_service;
...
for (;;)
{
  try
  {
    io_service.run();
    break; // run() exited normally
  }
  catch (my_exception& e)
  {
    // Deal with exception as appropriate.
  }
}