TridionPageProvider.GetContentByUrl throws null reference exception How do we specify the CD server?

Question

I am using DD4T to implement SDL Tridion. I have 2 servers (in Datacenters)

1. Content Management (Server A)
2. Content Delivery (Server B)

I have created a DD4T template in my local machine. In the DD4T Web Site, i have copied the lib and config directories. Now I am getting a runtime Error.

[NullReferenceException: Object reference not set to an instance of an object.]
   DD4T.Providers.SDLTridion2013.TridionPageProvider.GetContentByUrl(String Url) +547
   DD4T.Factories.PageFactory.TryFindPage(String url, IPage& page) +557
   DD4T.Mvc.Controllers.TridionControllerBase.GetModelForPage(String PageId) +109
   DD4T.Mvc.Controllers.TridionControllerBase.Page(String pageId) +22

I have few questions:

1. How the DD4T application finds the Content Delivery server (Server B), although it is not mentioned anywhere in the config file.
2. How to solve the above exception.
3. Can we provide Content Delivery URL in the DD4T Website and connect to it from Visual Studio, or do I need to set up a Content delivery instance in my local host environment?

Log errors

014-08-08 11:57:15,766 [21] DEBUG Performance [(null)] - >>TryFindPage (/Test_Page
2014-08-08 11:57:15,813 [21] DEBUG Performance [(null)] - about to load page from cache with key Page_/Test_Page_0
2014-08-08 11:57:15,814 [21] DEBUG Performance [(null)] - finished loading page from cache with key Page_/Test_Page_0, page found = False
2014-08-08 11:57:15,814 [21] DEBUG Performance [(null)] - about to load page content from provider with url /Test_Page
2014-08-08 11:57:15,820 [21] DEBUG Performance [(null)] - >>GetContentByUrl(/Test_Page)
2014-08-08 11:57:15,820 [21] DEBUG Performance [(null)] - GetContentByUrl: about to create query
2014-08-08 11:57:24,228 [21] DEBUG Performance [(null)] - GetContentByUrl: created query
2014-08-08 11:57:24,307 [21] DEBUG Performance [(null)] - GetContentByUrl: added criteria to query
2014-08-08 11:57:24,307 [21] DEBUG Performance [(null)] - GetContentByUrl: about to execute query
2014-08-08 11:57:24,309 [21] DEBUG Performance [(null)] - GetContentByUrl: executed query

Answer 1

1. DD4T is part of your website and runs on your Content Delivery (web)server. In the 'bin\config\cd_storage_conf.xml' there is a reference to the so called 'Broker Database'. This is the Tridion Content Delivery Databases that DD4T uses to find it's content. So your call GetContentByUrl tries to find it's content in this Broker Database.

2. Check Harald's comment. Did you follow the documentation? Java installed? License? Etc.

3. You can run/develop a DD4T website on any supported OS. You can either point your Visual Studio solution to an IIS website or use the build in webserver.