Re: [boost] asio socket connection state

13 Jan 2006


      ...
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On Thu, 12 Jan 2006, christopher baus wrote:
...
Also when a connection is closed by a peer during a read operation what
error should be expected?
eof, not_connected, fault, operation_aborted all seem reasonable.
For a TCP socket, I would expect it to return eof, since that is how TCP
sockets work.
I tested it on Windows and it does indeed return eof.  It might be worth
while to document this with the read functions.
Here's the class I'm using to track the socket state in my application
code.     I am setting the state in my event handlers (which is rather
error prone), but asio could manage it internally.

class stream_socket_connection_state
{
public:
  stream_socket_connection_state():state_(DISCONNECTED){}

  void connect()
  {
    if(DISCONNECTED == state_){
      state_ = CONNECTED_FOR_READ_AND_WRITE;
    }
    //
    // ignore attempts to reconnect socket
  }

  void shutdown_read()
  {
    if(CONNECTED_FOR_READ == state_){
      state_ = DISCONNECTED;
    }
    else if(CONNECTED_FOR_READ_AND_WRITE == state_){
      state_ = CONNECTED_FOR_WRITE;
    }
    //
    // ignore re-shutting down.
  }

  void shutdown_write()
  {
    if(CONNECTED_FOR_WRITE == state_){
      state_ = DISCONNECTED;
    }
    else if(CONNECTED_FOR_READ_AND_WRITE == state_){
      state_ = CONNECTED_FOR_READ;
    }
    //
    // ignore re-shutting down.
  }

  void disconnect()
  {
    state_ = DISCONNECTED;
  }

  //
  // Most apps only care if they can read or write
  // to a socket, but all states can be determined.
  bool connected_for_read()
  {
    return CONNECTED_FOR_READ || CONNECTED_FOR_READ_AND_WRITE;
  }
  bool connected_for_write()
  {
    return CONNECTED_FOR_WRITE || CONNECTED_FOR_READ_AND_WRITE;
  }

private:
  enum SOCKET_STATE
  {
    DISCONNECTED,
    CONNECTED_FOR_READ,
    CONNECTED_FOR_WRITE,
    CONNECTED_FOR_READ_AND_WRITE
  };

  SOCKET_STATE state_;
};