Re: [Boost-users] Synchronous problem with asio

Subject: Re: [Boost-users] Synchronous problem with asio
From: Dan Benèík (eubie_at_[hidden])
Date: 2009-08-11 09:37:17

Dear Zachary, 

thank you VERY MUCH. You can't imagine how much time I spent looking for an answer as simple as the one of yours! Finally my code works:)

All the best, 
Daniel.

<  ------------ Pùvodní zpráva ------------
<  Od: Zachary Turner <divisortheory_at_[hidden]>
<  Pøedmìt: Re: [Boost-users] Synchronous problem with asio
<  Datum: 11.8.2009 14:36:40
<  ----------------------------------------
<  2009/8/11 Dan Benèík <eubie_at_[hidden]>:
<  > Dear everybody,
<  > I have a problem using asio. My client/server application requires only
<  synchronous communication. So, using the examples for synchro from the boost
<  homepage, I have set up two procedures to send and receive data. Their code is
<  as follows:
<  >
<  > void vReceive(tcp::socket & socket, std::string & szDest){
<  >    char szTmp_Buf [BUF_LEN + 1];
<  >    szDest = "";
<  >    std::cout << "Entering vReceive . . ." << std::endl;
<  >
<  >    for (;;){
<  >      char szBuf [BUF_LEN];
<  >      boost::system::error_code error;
<  >      uInt uiBytes_Recv = socket.read_some(boost::asio::buffer(szBuf), error);
<  >      std::cout << " Read " << uiBytes_Recv << " bytes" << std::endl;
<  >      if (error == boost::asio::error::eof)
<  >         break; // Connection closed cleanly by peer.
<  >      else if (error)
<  >         throw boost::system::system_error(error); // Some other error.
<  >
<  >      memcpy((void*) szTmp_Buf, (void*) szBuf, uiBytes_Recv );
<  >      szTmp_Buf[ uiBytes_Recv ] = '\0';
<  >      szDest += szTmp_Buf;
<  >      };
<  >   std::cout << "Received" << szDest << std::endl;
<  >   std::cout << "Leaving vReceive . . ." << std::endl << std::endl;
<  >   };
<  >
<  > void vSend(tcp::socket & socket, std::string & szSrc){
<  >    std::cout << "Entering vSend . . . " << std::endl;
<  >    std::cout << "Sending " << szSrc << std::endl;
<  >    boost::system::error_code ignored_error;
<  >    boost::asio::write(socket, boost::asio::buffer(szSrc),
<  boost::asio::transfer_all(), ignored_error);
<  >    std::cout << "Leaving vSend . . . " << std::endl << std::endl;
<  >    };
<  >
<  >
<  > These procedures are just wrappers for the lines of code extracted from the
<  boost examples.
<  >
<  >
<  > In my test applications, the client calls
<  >
<  > vReceive(socket, szDate);
<  > vSend(socket, std::string("Chop Suey!") );
<  > vReceive(socket, szDate);
<  > vSend(socket, std::string("Halo"));
<  >
<  > and the server calls
<  >
<  > vSend(socket, message);
<  > vReceive(socket, szReceived);
<  > vSend(socket, message);
<  > vReceive(socket, szReceived);
<  >
<  > just to test the functionality. The problem is that both applications freeze
<  after the first information exchange, as I have depicted on the following
<  picture ( http://eubie.sweb.cz/asio_problem.JPG ). It seems that vReceive()
<  procedure on the client side doesn´t finish while vSend() finishes on the server
<  side. So, does anybody have any idea, what might be wrong?
<  >
<  > Just in case someone wanted to replicate the problem, I uploaded the complete
<  sources to http://eubie.sweb.cz/asio_problem.rar file.
<  >
<  > Thank you all in advance, Daniel.
<  > _______________________________________________
<  > Boost-users mailing list
<  > Boost-users_at_[hidden]
<  > http://lists.boost.org/mailman/listinfo.cgi/boost-users
<  >
<  
<  You're using boost::asio::write() to overcome the limitation of
<  socket.send() that it might not send all the data in one pass, so why
<  not do the same for reading?  Instead of making the loop yourself,
<  just use boost::asio::read().  Furthermore, you don't need to use the
<  completion condition version with transfer_all(), you can use the
<  alternate overload, which automatically does that for you.
<  
<  boost::asio::write(socket_, boost::asio::buffer(szOutput, szOutput.length()));
<  
<  boost::asio::read(socket_, boost::asio::buffer(szInput, szInput.length()));
<  
<  Short and sweet, that's all you need :)
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<  Boost-users_at_[hidden]
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<  
<  
<