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What's the difference in boost asio serial_port_service and serial_port

I have to implement a reliable rs232 asynchronous serial data transfer (over USB) (for reliable) - for both windows and Linux including esp. this wonderful embedded system called black big bone.

In the end, I just want to be able (compatible) to talk rs232 with reliable timeouts, cancel () reset (), etc., so that it doesn't crash / hang when, for example, the tx or rx line is accidentally disconnected. So I could just copy / paste / accept the existing examples. But I would also like to become more enlightened; -)

I decided to use boost: asio :: serial_port . Now, reading the docs, I'm confused by these two classes (well, three with typedef serial_port):

serial_port_service - The default service implementation for the serial port.

class serial_port_service : public io_service::service

basic_serial_port - Provides serial port functionality.

template< typename SerialPortService = serial_port_service>
class basic_serial_port :
  public basic_io_object< SerialPortService >,
  public serial_port_base

So I see that I need boost::asio::io_service

to build either boost::asio::serial_port

or serial_port_service

. I think I understand the basic approach of how asio does the job like these examples .

OK serial_port_service

comes from io_service, its ctor accepts io_service

, and its interface also offers those member members basic_serial_port

.

For me it looks like an io_service which also implements basic_serial_port - what is the reason for having both classes? When to use the one when the other? Not sure about the possibilities, and what about this serial_port

typedef. Maybe (well, obviously) I'm missing something - can someone give me more light?

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Often an application must use an I / O object. In this case it will be boost::asio::serial_port

.

Various classes are used to separate responsibilities and abstractions. The similarity in the names can be confusing, so the documentation is very careful about naming it. The documentation states:



The class io_service

implements an extensible, type-safe, polymorphic set of I / O services, indexed by the service type. A class object io_service

must be initialized before I / O objects such as sockets, resolvers, and timers can be used. These I / O objects differ in constructors that take a parameter io_service&

.

There are I / O services to manage the logical interface of the operating system on behalf of I / O objects. In particular, there are resources that are shared across the I / O object class. For example, timers can be implemented in terms of a single timer queue. I / O services manage these shared resources.

To explain this in the context of serial ports:

  • io_service

    provides an event loop and manages I / O services such as serial_port_service

    .
  • serial_port

    is an I / O object that provides an interface for performing serial port-related operations. The implementation is very simple:
    • Defines how information should be returned to the caller: throw, if an error occurs, fill std::future

      , suspend the coroutine , etc.
    • Cancels valid work with serial_port_service

      its I / O service.
    • Provides RAII semantics. When serial_port

      destroyed, it will cancel the outstanding asynchronous operations and close serial_port

      .
  • serial_port_service

    is the I / O service:
    • It provides an abstraction and implements a platform-specific API.
    • It is used in conjunction with serial_port

      that uses the same io_service

      . When serial_port

      created with io_service

      , serial_port

      will use an existing serial_port_service

      one registered with io_service

      , or create and register a new one serial_port_service

      with io_service

      .
    • It functions like a factory for an I / O object implementation

      . For serial_port

      this, most likely the underlying file descriptor or descriptor.
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