Re: [Boost-users] [ASIO] Wrong usage of streambuf ?

Subject: Re: [Boost-users] [ASIO] Wrong usage of streambuf ?
From: Imran Fanaswala (imran.fanaswala_at_[hidden])
Date: 2009-12-10 21:00:04

Axel-41 wrote:
> 
>   Hello
> 
> I m writing a simple client/server program. On a request the server 
> answers "ok\r\n". It works well. I have a problem with the client.
> Using async functions, I don't manage to handle the response from the 
> server. Once the server sent the response, I want to read the data, 
> close the socket, and open a new connection to the server.
> 
> When I don't read the data sent by the server, I manage to close the 
> socket and repeat the operation (close the socket, and reconnect to the 
> server).
> When I read the data, the program seems to block.
> 
> /* Callback to the async_write function. On any request, the server 
> sends "ok\r_n" */
> void Client::handle_write(boost::asio::ip::tcp::socket* socket, const 
> boost::system::error_code& err)
> {
>      if(!err)
>      {
>          cout << "Read..." << endl ;
>      // response_ is a boost::asio::streambuf variable
>          boost::asio::async_read_until(*socket, response_, "\r\n", 
> boost::bind(&Client::handle_read, this, socket, 
> boost::asio::placeholders::error, 
> boost::asio::placeholders::bytes_transferred)) ;
>      }
>      else
>      {
>          cout << "Error when writing to host: " << err.message() << "\n" ;
>      }
> }
> 
> void Client::handle_read(boost::asio::ip::tcp::socket* socket, const 
> boost::system::error_code& err, size_t bytes_transferred)
> {
>      cout << bytes_transferred << " bytes received. " << endl ;
> 
>      /* Dont count the 2 bytes long "\r\n" string */
>      int message_size = bytes_transferred - 2 ;
> 
> 
>      char * response_char = new char[message_size + 1] ;
>      response_char[message_size] = '\0' ;
>      response_stream.read(response_char, message_size) ;
>      string result(response_char) ;
>      delete response_char ;
>      response_.consume(2) ;
> 
>      socket->close() ;
>      delete socket ;
>      connect() ;
>      return ;
> }
> 
> If I skip the block where I read the response_ into a string, the 
> program works flawlessly. If I try to read the response from the 
> streambuf variable, the program is blocked at the next call to 
> async_read_until() */
> So I guess that I m doing something wrong with the streambuf variable 
> named "response_", but I dont understand what. Can someone explain me 
> what is wrong ?
> 
> Thanks in advance.
> 
> 
> 
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> 
> 

I am not really sure what response_stream is, but I see what you are trying
to do. Consider doing the following instead:

void Client::handle_read(boost::asio::ip::tcp::socket* socket, const
boost::system::error_code& err, size_t bytes_transferred)
{
...
  //Note: data, will contain the "ok\r\n".. so just do some string manip to
get rid of it
  const char* data=boost::asio::buffer_cast<const char*>(response_.data());

  response_.consume(bytes_transferred); //This is the key...
...
} 
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