PVS-Studio warning V547 for NetXMS

typedef UINT_PTR SOCKET;

static int DoRadiusAuth(....)
{
  SOCKET sockfd;
  ....
  // Open a socket.
  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0)
  {
    DbgPrintf(3, _T("RADIUS: Cannot create socket"));
    pairfree(req);
    return 5;
  }
  ....
}

This suspicious code was found in NetXMS project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'sockfd < 0' is always false. Unsigned type value is never < 0. radius.cpp 682

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