[Boost-users] [asio] tcp::socket state query?

From: Rod Morison (rod_at_[hidden])
Date: 2006-09-07 20:07:17

Is there way to query the local status of a socket in asio? Or, is  
there another technique for state & error management?

For example, something lick the TcpSocket state in Qt v4. I.e.,

AbstractSocket::UnconnectedState    0    The socket is not connected.
QAbstractSocket::HostLookupState    1    The socket is performing a  
host name lookup.
QAbstractSocket::ConnectingState    2    The socket has started  
establishing a connection.
QAbstractSocket::ConnectedState    3    A connection is established.
QAbstractSocket::BoundState    4    The socket is bound to an address  
and port (for servers).
QAbstractSocket::ClosingState    6    The socket is about to close  
(data may still be waiting to be written).
QAbstractSocket::ListeningState    5    For internal use only.

(from http://doc.trolltech.com/4.2/qabstractsocket.html#SocketState-enum)

Here's why I'm asking: I'm looking at the chat_client.cpp example.The  
socket is connected via async_connect in the chat_client constructor.  
If the first resolved endpoint fails to connect the handler tries an  
async_connect with the next endpoint.

First question: Are the async requests initiated under an io_servce  
(and executed by the run() method) queued in the order they are called  
via async_xxx calls? (I'm assuming/hoping that's a yes.)

So the issue I have with the chat_client design is as follows: because  
iterating the endpoint list (to connect the socket) is in a handler,  
what if another socket operation slipped in ahead of that handler, say  
a write (assuming the first endpoint failed)? I'd want the do_write()  
function to be able to check the socket state. I can do the state  
control myself via the handlers and a class state variable, but is  
there a better way? (Similarly, this app can happily go writing to an  
unconnected socket--I realize it's a sample, not production code, but  
I'm thinking through my _real_ app here.)

Hope this makes sense,

Rod