inet_pton Function

Header: ws2tcpip.h

Library: Ws2_32.lib

DLL: Ws2_32.dll

Syntax

            
INT
inet_pton(
  _In_  INT AddressFamily,
  _In_  PCSTR pszString,
  _Out_ PVOID pAddr
);
            
        

Parameters

AddressFamily: INT. The address family. For IPv4, specify AF_INET. For IPv6, specify AF_INET6.
pszString: PCSTR. A pointer to a null-terminated string that contains the IPv4 or IPv6 address to convert.
pAddr: PVOID. A pointer to a buffer that stores the converted IP address. The buffer must be large enough to hold the converted address, which depends on the AddressFamily parameter. For IPv4, this is a pointer to an IN_ADDR structure. For IPv6, this is a pointer to an IN6_ADDR structure.

Return Value

If the function succeeds, the return value is 1. The pszString parameter points to a valid IP address.

If the function fails, the return value is 0. The pszString parameter does not point to a valid IP address.

If an unknown flag is passed in the AddressFamily parameter, the return value is -1.

Remarks

The inet_pton function converts an IPv4 or IPv6 network address from its presentation (character) format to its numeric binary form.

This function is a more modern and preferred alternative to functions like inet_addr and inet_ntoa.

The pszString parameter can contain an IPv4 address in dotted-decimal notation (e.g., "192.168.1.1") or an IPv6 address (e.g., "::1", "2001:db8::1").

The pAddr parameter must point to a structure of the appropriate size for the specified AddressFamily:

For AF_INET, pAddr points to an IN_ADDR structure.
For AF_INET6, pAddr points to an IN6_ADDR structure.

Example

Converting an IPv4 Address

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

// Link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

int main() {
    WSADATA wsaData;
    INT iResult;
    char ipstr[INET_ADDRSTRLEN];
    struct sockaddr_in sa;

    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    const char *IP4toConvert = "192.168.1.1";

    iResult = inet_pton(AF_INET, IP4toConvert, &(sa.sin_addr));

    if (iResult > 0) {
        printf("inet_pton successful\n");
        // Convert the IP address back to a string for display
        inet_ntop(AF_INET, &(sa.sin_addr), ipstr, sizeof ipstr);
        printf("Converted IP: %s\n", ipstr);
    } else if (iResult == 0) {
        printf("inet_pton failed: invalid address string\n");
    } else {
        printf("inet_pton failed with error: %d\n", WSAGetLastError());
    }

    WSACleanup();
    return 0;
}
                
            

Converting an IPv6 Address

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

// Link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

int main() {
    WSADATA wsaData;
    INT iResult;
    char ipstr[INET6_ADDRSTRLEN];
    struct sockaddr_in6 sa6;

    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    const char *IP6toConvert = "2001:db8::1";

    iResult = inet_pton(AF_INET6, IP6toConvert, &(sa6.sin6_addr));

    if (iResult > 0) {
        printf("inet_pton successful\n");
        // Convert the IP address back to a string for display
        inet_ntop(AF_INET6, &(sa6.sin6_addr), ipstr, sizeof ipstr);
        printf("Converted IP: %s\n", ipstr);
    } else if (iResult == 0) {
        printf("inet_pton failed: invalid address string\n");
    } else {
        printf("inet_pton failed with error: %d\n", WSAGetLastError());
    }

    WSACleanup();
    return 0;
}
                
            

Requirements

Minimum supported client: Windows Vista [desktop apps | UWP apps]

Minimum supported server: Windows Server 2008 [desktop apps | UWP apps]

Header: ws2tcpip.h

Library: Ws2_32.lib

DLL: Ws2_32.dll