You need to use the same httpClient to be able to control the session correctly.
Try these steps, referring to a generic LoginActivity
public static DefaultHttpClient httpClient;
Initialize it for the first time as follows.
URL url=new URL(urlToHit);
LoginScreen.httpClient = new DefaultHttpClient(); //LoginScreen is the name of the current Activity
HttpPost httppost = new HttpPost(url.toString());
HttpResponse response = LoginScreen.httpClient.execute(httppost);
Now for all further connections I used the same httpClient For example in the next activity.
URL url=new URL(urlToHit);
HttpPost httppost = new HttpPost(url.toString());
HttpResponse response = LoginScreen.httpClient.execute(httppost);
I haven't tested this, but I remember i had to face the same problem and i solved it storing the httpClient and using always that one.
Source: http://www.lightrains.com/blog/simple-tip-session-handling-android