How do I find the current IP address(es) of my machine?

You can use GetComputerName (or gethostname) and gethostbyname (see WINSOCK2.H) for this. Remember that a computer can have more than one IP address - it can have multiple adapters, or be supporting extra addresses for RAS purposes.

Bear in mind that this code uses Winsock functionality, so a successful call to WSAStartup is a pre-requisite.

HOSTENT* phe ;
char szCpuName [128] ;
DWORD dwSize = sizeof(szCpuName);
int iaddr, ifield;
UINT uField;

CString csIpAddr;
CString csAddrField;

if (GetComputerName (szCpuName, &dwSize) == 0)
   wsprintf (szCpuName, "Can't get computer name, error %d",
   GetLastError ());
   AfxMessageBox (szCpuName);
   phe = gethostbyname (szCpuName);
   if (phe != NULL)
      for (iaddr=0; phe->h_addr_list[iaddr] != NULL; iaddr++)
         csIpAddr = "";
         for (ifield=0; 
              ifield < phe->h_length; 
            if (ifield > 0)
               csIpAddr += ".";

            uField = ((BYTE*)phe->h_addr_list[iaddr])[ifield];
            csAddrField.Format("%u", uField);
            csIpAddr += csAddrField;
         // Do what you want with the address here. I add it to a listbox.
         m_ctrlListbox.AddString (csIpAddr);