Getting always error 404 on jsonp request

I ran into an issue while trying to retrieve some jsonp data from another Host. That's my setup:

Client on 192.168.2.107 running on Raspbian

Host on 192.168.2.109 running apache2 on raspbian

Client is able to get the web Page pump.php from Host via Web Browser.

Code on Client:

$.ajax({
   url: 'http://192.168.2.109/pump.php',
   dataType: 'jsonp',
   success:function(result)        {
             console.log(result);
           },
   error:function (xhr, ajaxOptions, thrownError) { 
            console.log(xhr);
            alert(thrownError + xhr.status);
         }
});

Code on server (pump.php):

header("Content-Type: application/json");
echo "myCall({foo:'bar'});";

I always get a 404 response from the host. Though I'm completely out of ideas what's wrong with my code or something else or even how I should try to troubleshoot this, any help is higly appreciated! Thanks in advance.

[EDIT] Forgot to mention that myCall() is specified in the client as well:

function myCall(data) {
  console.log(data);
}