static char *ot_tcp_socket_error(Socket sock)
static const char *ot_tcp_socket_error(Socket sock)
static char *ot_tcp_socket_error(Socket sock){    Actual_Socket s = (Actual_Socket) sock;    static char buf[128];    if (s->error == kOTNoError)	return NULL;    sprintf(buf, "error %d", s->error);    return buf;}