Trouble with session ID and Drupal cookies when trying to establish a connection with Service Module and http-post

Question

I am trying to complete an http-post between my common lisp application and my Drupal Site running Services and a Rest server. Currently I have my rest server set up to accept user login, and using Poster (Firefox plugin to create http requests) I am able to connect to my rest server. Also, using Poster if I am currently logged in I get a response "406 Not Acceptable: Already logged in as.." and if I am not logged in I get "200 OK" and when I go back to my browser I am logged in to my Drupal site.

Now I have been trying to simulate this same behavior using an http-post from my lisp application and I have been having a lot of trouble. For a long time I was always getting "200 OK" if I had correct username and password in the body of my post looking something like this:

username=ender2012&password=password&form_id=user_login

but it would not actually login and if I was already logged in I would never receive the 406 response that I expected. Finally I downloaded HttpFox which showed me the actual post that Poster was sending and I noticed that Poster was sending a Cookie header that looked like this

Cookie: Drupal.toolbar.collapsed=1; CAKEPHP=10e32669174a611c8919eeff471a2a1c; Drupal.tableDrag.showWeight=0; has_js=1; SESSdc0685ed01f285dab628a3700259e6bc=3qqK5XPaLRhEx7o4wAbIq5qK9qHEzRxz5qUnYZsaXG0

Now if I add a Cookie header to my lisp application's post with the Cookie I saw in http-post from Poster and I am logged in, I will get the 406. So it seems that there is some sort of session information stored in this cookie that I will need to use for my lisp application but I am unsure about how this would all work inside my application. Could anyone help me understand all of this?

Details:

• I am running Drupal 7

• I am using Services 3.0

• I am using a rest server with session authentication

• I am using application/x-www-form-urlencoded

• I am running this server on MAMP localhost currently