inet_ntop function
The inet_ntop function converts an Internet Protocol (IP) address structure to a string. This function is more robust and extensible than the IPv6-compatible AddressTo-String conversion functions.
Syntax
PCSTR inet_ntop(
INT Family,
const void *pAddr,
PSTR pStringBuf,
socklen_t StringBufSize
);
Parameters
| Parameter | Description |
|---|---|
Family |
The address family. Possible values are specified in the Winsock2.h header. |
pAddr |
A pointer to a buffer containing the IP address structure. |
pStringBuf |
A pointer to a buffer to store the string representation of the IP address. |
StringBufSize |
The size, in bytes, of the buffer pointed to by pStringBuf. |
Return value
If the function succeeds, it returns a pointer to the buffer pointed to by pStringBuf.
If the function fails, it returns NULL. To get extended error information, call WSAGetLastError.
Remarks
The inet_ntop function converts an IP address structure to a presentation string. This function supports both IPv4 and IPv6 addresses. The Family parameter specifies the address family.
For IPv4 addresses, the pAddr parameter points to an in_addr structure. For IPv6 addresses, it points to an in6_addr structure.
The pStringBuf parameter must point to a buffer large enough to hold the resulting string. For IPv4, a buffer of 16 bytes is sufficient. For IPv6, a buffer of 40 bytes is recommended.
Prior to Windows Vista, the inet_ntop function was not available. For backward compatibility on earlier versions of Windows, you may need to use the inet_ntoa function for IPv4 addresses and other methods for IPv6.
Example
// Example of using inet_ntop for IPv4
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
int main() {
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct in_addr ipv4Addr;
char ipStringBuf[INET_ADDRSTRLEN];
PCSTR pszAddress;
// Convert IPv4 address "192.168.1.1" to string
inet_pton(AF_INET, "192.168.1.1", &ipv4Addr);
pszAddress = inet_ntop(AF_INET, &ipv4Addr, ipStringBuf, INET_ADDRSTRLEN);
if (pszAddress != NULL) {
printf("IPv4 Address: %s\n", pszAddress);
} else {
printf("inet_ntop failed with error: %d\n", WSAGetLastError());
}
WSACleanup();
return 0;
}
// Example of using inet_ntop for IPv6
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
int main() {
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct in6_addr ipv6Addr;
char ipStringBuf[INET6_ADDRSTRLEN];
PCSTR pszAddress;
// Convert IPv6 address "2001:db8::1" to string
inet_pton(AF_INET6, "2001:db8::1", &ipv6Addr);
pszAddress = inet_ntop(AF_INET6, &ipv6Addr, ipStringBuf, INET6_ADDRSTRLEN);
if (pszAddress != NULL) {
printf("IPv6 Address: %s\n", pszAddress);
} else {
printf("inet_ntop failed with error: %d\n", WSAGetLastError());
}
WSACleanup();
return 0;
}