Sockets

This is a discussion on Sockets within the Networking/Device Communication forums, part of the General Programming Boards category; After visiting sites like MadWizard, ProgrammersHeaven, etc., I'm still having a lot of trouble with sockets programming. Almost all tutorials ...

  1. #1
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    Sockets

    After visiting sites like MadWizard, ProgrammersHeaven, etc., I'm still having a lot of trouble with sockets programming. Almost all tutorials seem contradictory, so I need to ask for help here...

    Can anyone show me a very, very simple code, annotated, that'll show me how to send a message from one program to another, using sockets, by opening a connection ? Thanks for your help.

  2. #2
    Disturbed Boy gustavosserra's Avatar
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    There is a very good tutorial at:
    http://www.ecst.csuchico.edu/~beej/guide/net/
    Try to read this one.
    Nothing more to tell about me...
    Happy day =)

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    Guest Sebastiani's Avatar
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    The socket API is very small, containing just a handful of core functions. Windows sockets mostly mirror Berkley sockets, but also add an even more complicated layer on top of taht, obscuring things just a bit more.
    At first, just focus on the core functions and the underlying framework. Some of the data types are identical in size but different in their interpretation of the (same) data (data - such as port numbers and bind addresses - have to be stored in these data structures in network byte order for the code to work properly (but not the the sent/recieved data - the TCPIP stack will take care of that)).
    Also, several uniouns are used to (supposedly) make your life easier when you get around to messing with subnets, etc.
    And as far as sending and recieving data goes, you have to be keep reading or writing till the buffers are filled or emptied to ensure proper transmission. Sometimes the connection is suddenly closed for some reason, so you have to be prepared for that too. Also, be sure to read through your header docs- there's a whole lot of useful info in there as well.
    Code:
    bool fun(bool value)
    {
        return std::pow(std::exp(1), std::complex<float>(0, 1) 
        * std::complex<float>(std::atan(1)*(1 << (value + 2))))
        .real() > 0;
    }

  4. #4
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    I find the Beej tutorial not so good to begin Sockets, as it goes through a lot of things that assume you know what is being said. For example, you're not given an easy code showing simple socket functions and how they work, but a lot at once and it's all almost thrown at you. I still can't write, after reading the tutorial many times, a simple program allowing me to send a message over a network...

  5. #5
    WDT
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    Actually Korhedron raises something I am still to get round to as of yet. There seems to be no C++ standard sockets though there are programs out there written in C++.I'll get round to socket programming but right now I'm moving to file I/O and STL. Would just like to know if there is a standard C++ socket API? FYI I have done some light C sockets but as I normally do C programming in UNIX (and rarely Linux) I see I may have trouble converting these little progs to windows code.
    A hundred Elephants can knock down the walls of a fortress... One diseased rat can kill everyone inside

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    Guest Sebastiani's Avatar
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    Code:
     bool connect(SOCKET socket, unsigned long address, unsigned short port)
    {
     sockaddr_in remote = {0};
     remote.sin_family = AF_INET;
     remote.sin_port = htons(port);
     remote.sin_addr.S_un.S_addr = htonl(address);
     return SOCKET_ERROR != ::connect(socket, (sockaddr*)&remote, sizeof(remote));
    }
    Code:
    bool fun(bool value)
    {
        return std::pow(std::exp(1), std::complex<float>(0, 1) 
        * std::complex<float>(std::atan(1)*(1 << (value + 2))))
        .real() > 0;
    }

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    If your doing windows-programming you need to init you winsock before using it.

    Code:
    bool initWinsocket()
    {
      WORD wVersionRequested;
      WSADATA wsaData;
      int err;
     
      wVersionRequested = MAKEWORD( 2, 2 );
      err = WSAStartup( wVersionRequested, &wsaData );
      if ( err != 0 ) {
          return -1;
      }
     
      if ( LOBYTE( wsaData.wVersion ) != 2 || 
           HIBYTE( wsaData.Version ) != 2 ) {
          WSACleanup( );
          return -1; 
      }
       return 0;
      /* The WinSock DLL is acceptable. Proceed. */
    }
    Source :msdn

  8. #8
    Banned nickname_changed's Avatar
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    >>If your doing windows-programming you need to init you winsock before using it.

    Yep, beej covers that near the start of the book. When I was learning sockets I read a book all about networking (can't remember the name... was a white book with black text, something like Networking or Internetworking was one of the words... author started with a C I think). It was good because it covered everything about how networks work, then showed some code. Then I read beej and everything was dandy.

    Although beej does attempt to cover things like how IP addresses work (I think he does), his book still seems to require that you have a good understanding of how networking works down to the socket layer.

    I'd love to see a C++ standard sockets library, but I doubt it will happen for a long time.

  9. #9
    Registered User trainee's Avatar
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    Originally posted by WDT
    Actually Korhedron raises something I am still to get round to as of yet. There seems to be no C++ standard sockets though there are programs out there written in C++.I'll get round to socket programming but right now I'm moving to file I/O and STL. Would just like to know if there is a standard C++ socket API? FYI I have done some light C sockets but as I normally do C programming in UNIX (and rarely Linux) I see I may have trouble converting these little progs to windows code.
    No there is currently no socket API in the STL. I heard somewhere they were thinking about adding it though.

    trainee

  10. #10
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    This thread is allready a little old but since i came accross this problem many times also and it took me about 30min to find these 2 sites i think its worth noting them.

    http://www.manualy.sk/sock-faq/unix-socket-faq.html

    http://www.developerweb.net/sock-faq/ (the old faq)
    http://www.developerweb.net/forum/ (same site, now in a forum)

    I found them extensive enough to cover most of the unclear things anybody i know came up with until now.
    For example SO_REUSEADDR

    Chris

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