ADDRINFOW structure (ws2def.h)

The addrinfoW structure is used by the GetAddrInfoW function to hold host address information.

Syntax

typedef struct addrinfoW {
  int              ai_flags;
  int              ai_family;
  int              ai_socktype;
  int              ai_protocol;
  size_t           ai_addrlen;
  PWSTR            ai_canonname;
  struct sockaddr  *ai_addr;
  struct addrinfoW *ai_next;
} ADDRINFOW, *PADDRINFOW;

Members

ai_flags

Type: int

Flags that indicate options used in the GetAddrInfoW function.

Supported values for the ai_flags member are defined in the Winsock2.h header file and can be a combination of the options listed in the following table.

ai_family

Type: int

The address family. Possible values for the address family are defined in the Winsock2.h header file.

On the Windows SDK released for Windows Vista and later,, the organization of header files has changed and the possible values for the address family are defined in the Ws2def.h header file. Note that the Ws2def.h header file is automatically included in Winsock2.h, and should never be used directly.

The values currently supported are AF_INET or AF_INET6, which are the Internet address family formats for IPv4 and IPv6. Other options for address family (AF_NETBIOS for use with NetBIOS, for example) are supported if a Windows Sockets service provider for the address family is installed. Note that the values for the AF_ address family and PF_ protocol family constants are identical (for example, AF_UNSPEC and PF_UNSPEC), so either constant can be used.

The following table lists common values for the address family although many other values are possible.

ai_socktype

Type: int

The socket type. Possible values for the socket type are defined in the Winsock2.h include file.

The following table lists the possible values for the socket type supported for Windows Sockets 2.

In Windows Sockets 2, new socket types were introduced. An application can dynamically discover the attributes of each available transport protocol through the WSAEnumProtocols function. So an application can determine the possible socket type and protocol options for an address family and use this information when specifying this parameter. Socket type definitions in the Winsock2.h and Ws2def.h header files will be periodically updated as new socket types, address families, and protocols are defined.

In Windows Sockets 1.1, the only possible socket types are SOCK_DATAGRAM and SOCK_STREAM.

ai_protocol

Type: int

The protocol type. The possible options are specific to the address family and socket type specified. Possible values for the ai_protocol are defined in Winsock2.h and the Wsrm.h header files.

On the Windows SDK released for Windows Vista and later,, the organization of header files has changed and this member can be one of the values from the IPPROTO enumeration type defined in the Ws2def.h header file. Note that the Ws2def.h header file is automatically included in Winsock2.h, and should never be used directly.

If a value of 0 is specified for ai_protocol, the caller does not wish to specify a protocol and the service provider will choose the ai_protocol to use. For protocols other than IPv4 and IPv6, set ai_protocol to zero.

The following table lists common values for the ai_protocol member although many other values are possible.

If the ai_family member is AF_IRDA, then the ai_protocol must be 0.

ai_addrlen

Type: size_t

The length, in bytes, of the buffer pointed to by the ai_addr member.

ai_canonname

Type: PWSTR

The canonical name for the host.

ai_addr

Type: struct sockaddr*

A pointer to a sockaddr structure. The ai_addr member in each returned ADDRINFOW structure points to a filled-in socket address structure. The length, in bytes, of each returned ADDRINFOW structure is specified in the ai_addrlen member.

ai_next

Type: struct addrinfoW*

A pointer to the next structure in a linked list. This parameter is set to NULL in the last addrinfoW structure of a linked list.

Remarks

The addrinfoW structure is used by the Unicode GetAddrInfoW function to hold host address information.

The addrinfo structure is ANSI version of this structure used by the ANSI getaddrinfo function.

Macros in the Ws2tcpip.h header file define a ADDRINFOT structure and a mixed-case function name of GetAddrInfo. The GetAddrInfo function should be called with the nodename and servname parameters of a pointer of type TCHAR and the hints and res parameters of a pointer of type ADDRINFOT. When UNICODE or _UNICODE is defined, ADDRINFOT is defined to the addrinfoW structure and GetAddrInfo is defined to GetAddrInfoW, the Unicode version of this function. When UNICODE or _UNICODE is not defined, ADDRINFOT is defined to the addrinfo structure and GetAddrInfo is defined to getaddrinfo, the ANSI version of this function.

Upon a successful call to GetAddrInfoW, a linked list of ADDRINFOW structures is returned in the ppResult parameter passed to the GetAddrInfoW function. The list can be processed by following the pointer provided in the ai_next member of each returned ADDRINFOW structure until a NULL pointer is encountered. In each returned ADDRINFOW structure, the ai_family, ai_socktype, and ai_protocol members correspond to respective arguments in a socket or WSASocket function call. Also, the ai_addr member in each returned ADDRINFOW structure points to a filled-in socket address structure, the length of which is specified in its ai_addrlen member.

Examples

The following code example shows how to use the addrinfoW structure.

#ifndef UNICODE
#define UNICODE
#endif

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>

#pragma comment(lib, "Ws2_32.lib")

int __cdecl wmain(int argc, wchar_t ** argv)
{
//--------------------------------
// Declare and initialize variables.
    WSADATA wsaData;
    int iResult;

    ADDRINFOW *result = NULL;
    ADDRINFOW *ptr = NULL;
    ADDRINFOW hints;

    DWORD dwRetval = 0;
    int i = 1;

    struct sockaddr_in *sockaddr_ipv4;
    struct sockaddr_in6 *sockaddr_ipv6;
//    LPSOCKADDR sockaddr_ip;

    wchar_t ipstringbuffer[46];

    // Validate the parameters
    if (argc != 3) {
        wprintf(L"usage: %ws <hostname> <servicename>\n", argv[0]);
        wprintf(L"       provides protocol-independent translation\n");
        wprintf(L"       from a host name to an IP address\n");
        wprintf(L"%ws example usage\n", argv[0]);
        wprintf(L"   %ws www.contoso.com 0\n", argv[0]);
        return 1;
    }
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0) {
        wprintf(L"WSAStartup failed: %d\n", iResult);
        return 1;
    }
//--------------------------------
// Setup the hints address info structure
// which is passed to the GetAddrInfoW() function
    memset(&hints, 0, sizeof (hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    wprintf(L"Calling GetAddrInfoW with following parameters:\n");
    wprintf(L"\tName = %ws\n", argv[1]);
    wprintf(L"\tServiceName (or port) = %ws\n\n", argv[2]);

//--------------------------------
// Call GetAddrInfoW(). If the call succeeds,
// the aiList variable will hold a linked list
// of addrinfo structures containing response
// information about the host
    dwRetval = GetAddrInfoW(argv[1], argv[2], &hints, &result);

    if (dwRetval != 0) {
        wprintf(L"GetAddrInfoW failed with error: %d\n", dwRetval);
        WSACleanup();
        return 1;
    }
    wprintf(L"GetAddrInfoW returned success\n");

    // Retrieve each address and print out the hex bytes
    for (ptr = result; ptr != NULL; ptr = ptr->ai_next) {

        wprintf(L"GetAddrInfoW response %d\n", i++);
        wprintf(L"\tFlags: 0x%x\n", ptr->ai_flags);
        wprintf(L"\tFamily: ");
        switch (ptr->ai_family) {
        case AF_UNSPEC:
            wprintf(L"Unspecified\n");
            break;
        case AF_INET:
            wprintf(L"AF_INET (IPv4)\n");
            // the InetNtop function is available on Windows Vista and later
            sockaddr_ipv4 = (struct sockaddr_in *) ptr->ai_addr;
            wprintf(L"\tIPv4 address %ws\n",
                    InetNtop(AF_INET, &sockaddr_ipv4->sin_addr, ipstringbuffer,
                             46));

            // We could also use the WSAAddressToString function
            // sockaddr_ip = (LPSOCKADDR) ptr->ai_addr;
            // The buffer length is changed by each call to WSAAddresstoString
            // So we need to set it for each iteration through the loop for safety
            // ipbufferlength = 46;
            // iRetval = WSAAddressToString(sockaddr_ip, (DWORD) ptr->ai_addrlen, NULL, 
            //    ipstringbuffer, &ipbufferlength );
            // if (iRetval)
            //    wprintf(L"WSAAddressToString failed with %u\n", WSAGetLastError() );
            // else    
            //    wprintf(L"\tIPv4 address %ws\n", ipstringbuffer);
            break;
        case AF_INET6:
            wprintf(L"AF_INET6 (IPv6)\n");
            // the InetNtop function is available on Windows Vista and later
            sockaddr_ipv6 = (struct sockaddr_in6 *) ptr->ai_addr;
            wprintf(L"\tIPv6 address %ws\n",
                    InetNtop(AF_INET6, &sockaddr_ipv6->sin6_addr,
                             ipstringbuffer, 46));

            // We could also use WSAAddressToString which also returns the scope ID
            // sockaddr_ip = (LPSOCKADDR) ptr->ai_addr;
            // The buffer length is changed by each call to WSAAddresstoString
            // So we need to set it for each iteration through the loop for safety
            // ipbufferlength = 46;
            //iRetval = WSAAddressToString(sockaddr_ip, (DWORD) ptr->ai_addrlen, NULL, 
            //    ipstringbuffer, &ipbufferlength );
            //if (iRetval)
            //    wprintf(L"WSAAddressToString failed with %u\n", WSAGetLastError() );
            //else    
            //    wprintf(L"\tIPv6 address %ws\n", ipstringbuffer);
            break;
        default:
            wprintf(L"Other %ld\n", ptr->ai_family);
            break;
        }
        wprintf(L"\tSocket type: ");
        switch (ptr->ai_socktype) {
        case 0:
            wprintf(L"Unspecified\n");
            break;
        case SOCK_STREAM:
            wprintf(L"SOCK_STREAM (stream)\n");
            break;
        case SOCK_DGRAM:
            wprintf(L"SOCK_DGRAM (datagram) \n");
            break;
        case SOCK_RAW:
            wprintf(L"SOCK_RAW (raw) \n");
            break;
        case SOCK_RDM:
            wprintf(L"SOCK_RDM (reliable message datagram)\n");
            break;
        case SOCK_SEQPACKET:
            wprintf(L"SOCK_SEQPACKET (pseudo-stream packet)\n");
            break;
        default:
            wprintf(L"Other %ld\n", ptr->ai_socktype);
            break;
        }
        wprintf(L"\tProtocol: ");
        switch (ptr->ai_protocol) {
        case 0:
            wprintf(L"Unspecified\n");
            break;
        case IPPROTO_TCP:
            wprintf(L"IPPROTO_TCP (TCP)\n");
            break;
        case IPPROTO_UDP:
            wprintf(L"IPPROTO_UDP (UDP) \n");
            break;
        default:
            wprintf(L"Other %ld\n", ptr->ai_protocol);
            break;
        }
        wprintf(L"\tLength of this sockaddr: %d\n", ptr->ai_addrlen);
        wprintf(L"\tCanonical name: %s\n", ptr->ai_canonname);
    }

    FreeAddrInfo(result);
    WSACleanup();

    return 0;
}

Requirements

See also

GetAddrInfoEx

GetAddrInfoW

WSAEnumProtocols

addrinfo

addrinfoex

addrinfoex2

getaddrinfo

sockaddr