Visual C++ Network: How to get the local IP address(es)?

[Andreas Masur]

Q: How to get the local IP address(es)?

A: The following example will get up to ten assigned IP addresses...


#include <winsock2.h>

// Add 'ws2_32.lib' to your linker options

WSADATA WSAData;

// Initialize winsock dll
if(::WSAStartup(MAKEWORD(1, 0), &WSAData))
{
// Error handling
}

// Get local host name
char szHostName[128] = "";

if(::gethostname(szHostName, sizeof(szHostName)))
{
// Error handling -> call 'WSAGetLastError()'
}

// Get local IP addresses
struct sockaddr_in SocketAddress;
struct hostent *pHost = 0;

pHost = ::gethostbyname(szHostName);
if(!pHost)
{
// Error handling -> call 'WSAGetLastError()'
}

char aszIPAddresses[10][16]; // maximum of ten IP addresses

for(int iCnt = 0; ((pHost->h_addr_list[iCnt]) && (iCnt < 10)); ++iCnt)
{
memcpy(&SocketAddress.sin_addr, pHost->h_addr_list[iCnt], pHost->h_length);
strcpy(aszIPAddresses[iCnt], inet_ntoa(SocketAddress.sin_addr));
}

// Cleanup
WSACleanup();

As with everything, there exists of course other ways and other information which can be retrieved...some examples can be found in the following knowledge base article (http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/Q129/3/15.asp&NoWebContent=1).
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