$http({
  url:'http://xxx.xxx.xxx.xxx:8080/login',
  method:"POST",
  data:{user:$scope.user, password:$scope.password}
})

$app->post('/login', function ($request, $response) {
  //Parametros que se pasan a la api
  $input  = $request->getParsedBody();
  $req = $input['usuario'];
  $md5pass = md5($input['password']);
  $sth = $this->db->prepare("query");
  //bindParam pasandole los parametros para evitar injecciones sql
  $sth->bindParam("password", md5($input['password']));
  $sth->bindParam("usuario", $input['usuario']);
  $sth->execute();
  $todos = $sth->fetchAll();
  $cliente_id = $todos->cliente_id;
   ....

OPTIONS http://xxx.xxx.xxx.xxx:8080/login net::ERR_CONNECTION_REFUSED