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Asked: 2026-05-11T05:55:19+00:00

I am trying to implement a function called inet_pton which will convert a string

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I am trying to implement a function called ‘inet_pton’ which will convert a string representation of an IPv4 or IPv6 (like ‘66.102.1.147’ [google]) into binary network-byte ordered form. Here is the relevant part of my code:

#if defined WIN32 int inet_pton (int af, const char *src, void *dst)  {     const void *data;     size_t      len;     struct      addrinfo hints, *res;      hints.ai_family   = af;     hints.ai_socktype = SOCK_STREAM;      hints.ai_protocol = IPPROTO_UDP;     hints.ai_flags    = AI_NUMERICHOST;      if (getaddrinfo (src, NULL, &hints, &res))     {         std::cout << 'ERROR : inet_pton() in ' << __FILE__ << ' at line ' << __LINE__ << std::endl;         std::cout << '      : getaddrinfo() failed to get IP address info for \'' << src << '\'' << std::endl;         return 0;     } ...

So src is the incoming IP string. However, I always get an error like

getaddrinfo() failed to get IP address info for ‘66.102.1.147’

Can anyone with winsock experience comment? I also tried another method, the function

WSAStringToAddress ((LPTSTR)src, af, NULL, (LPSOCKADDR) &sa, &address_length)

But it always returns the error code WSAEINVAL, indicating an invalid IP string. This makes no sense to me. I’m using VS2005 as my IDE.

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1 Answer

  1. Well, for a start you’re asking for a stream socket with UDP as a protocol and that just isn’t going to happen.

    Try with:

    hints.ai_family   = af; hints.ai_socktype = 0;  hints.ai_protocol = 0; hints.ai_flags    = AI_NUMERICHOST;

    and memset it to zero first as it has extra members that you’re not setting…

    Also in my code I pass an empty string for the port or service when I don’t have one rather than a null. The docs don’t seem to specify what to do when you don’t have a value; but either way an empty string works for me.

    Oh, and as always in these situations, it would be useful to know what value WSAGetLastError() returns…

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