Resolving Hostname Using getaddrinfo(...) :: Winsock

This is a discussion on Resolving Hostname Using getaddrinfo(...) :: Winsock within the Windows Programming forums, part of the Platform Specific Boards category; Hi. I am new to winsock program and has began study from Network Programming for Microsoft Windows, Second Edition by ...

  1. #1
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    Nov 2001
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    Resolving Hostname Using getaddrinfo(...) :: Winsock

    Hi.

    I am new to winsock program and has began study from Network Programming for Microsoft Windows, Second Edition by Anthony Jones and Jim Ohlund.

    I am trying to get a code to basically resolve a hostname to its ip address. For example:

    -----
    user input: www.microsoft.com
    app output: 207.46.230.220
    -----

    I am able to get the calculation above working using older winsock 1.1+ tool including the use of structure hostent, gethostbyname(), and inet_ntoa().

    However, in their book, Jones and Ohlund recommend using the newer winsock tools including getaddrinfo() and getnameinfo(). I cannot figure out how to extract the corresponding IP address from a hostname. Here is the code:

    -----
    int rc = 0;
    addrinfo hints, *result = NULL;
    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = AI_CANONNAME;
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    if (getaddrinfo(rHName, "21", &hints, &result) != 0)
    return false;
    else
    {

    // This is where I need help getting the IP address

    m_sIP = (reinterpret_cast<sockaddr *>(result->ai_addr)->sa_data());// ->sa_data(); // inet_ntoa(*(reinterpret_cast<in_addr *>(host->h_addr)));

    return = true;
    }
    -----

    In the code above, m_sIP is a character array. What do I have to cast result->ai_addr in order to access the IP address?

    Thanks,
    Kuphryn

  2. #2
    Registered User
    Join Date
    Nov 2001
    Posts
    1,348
    Here is the solution to my original problem.

    -----
    {
    m_bVeri = false;

    addrinfo hints, *result = NULL;
    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = AI_PASSIVE;
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    if (getaddrinfo(static_cast<LPCTSTR>(rHName), m_sPort.c_str(), &hints, &result) != 0)
    return m_bVeri;

    if (getnameinfo(result->ai_addr, result->ai_addrlen, m_sIP, 256, NULL, 0, NI_NUMERICHOST) != 0)
    return m_bVeri;

    m_bVeri = true;
    freeaddrinfo(result);

    return m_bVeri;
    }

    Kuphryn

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