Basic way to get local IP

The function is as follow:

BOOL getLocalIP(CString &cstrIP)

{

    char strHostname[MAX_PATH] = {0};

    hostent* pHost = NULL;

 

    if (SOCKET_ERROR == gethostname(strHostname, sizeof(strHostname)))

       return FALSE;

 

    if (NULL == (pHost = gethostbyname(strHostname)))

       return FALSE;

 

    cstrIP = inet_ntoa(*(in_addr*)pHost->h_addr_list[0]);

    return !cstrIP.IsEmpty();

}

 

Remarks:

inet_ntoa():

· The string returned by inet_ntoa() resides in the memory allocate by windows sockets, we don’t need to free the string.

· The string is guaranteed to be valid until the next Windows Sockets function call within the same thread—but no longer. Therefore, the data should be copied immediately.

hostent:

struct  hostent {

        char    FAR * h_name;           /* official name of host */

        char    FAR * FAR * h_aliases;  /* alias list */

        short   h_addrtype;             /* host address type */

        short   h_length;               /* length of address */

        char    FAR * FAR * h_addr_list; /* list of addresses */

#define h_addr  h_addr_list[0]          /* address, for backward compat */

};

Notes: #define doesn’t limited to spacename.

And the structure returned by gethostbyname shouldn’t be changed.