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What exactly these lines do individually and collectively in JSON parsing

I am wondering after I searched in few books and on web that none of then detailed about it. I want to know that what exactly the purpose of below line individually while we parse JSON response file :
Lines ARE :
DefaultHttpClient client=new DefaultHttpClient();
HttpPost post = new HttpPost(Url);
HttpResponse response = client.execute(post);
HttpEntity entity = response.getEntity();
I know one thing that all together these four lines perform the connection with the server, but have no idea what individually the do.
I am sure I will get answer here from one of SOF besties.

Android's DefaultHttpClient Supports:
HTTPS, streaming uploads and downloads, configurable timeouts, IPv6 and connection pooling.
HttpPost :
The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line.
HttpResponse :
Takes care of the response that is got after executing client.execute(post);
Finally the following code obtains the message entity of this response.
response.getEntity()
Please check the android documentation for detailed implementation.

Code above is resposible for Http post request to server and get JSON response, so that you can parse and get required data.

Above 4 lines don't do JSON parsing. They only make an HTTP connection and the way of doing it is only recommended below Gingerbread. For Gingerbread and above use HttpURLConnection. More details here.
After you have the content (make a check if the response code is as expected - 200 or 201) you can proceed to JSON parsing. Use either Jackson, GSON or Android's json framework (this is my preferred order).

As per may Opinion
DefaultHttpClient client=new DefaultHttpClient(); responsible for HttpsURLConnection efficient(Connection) when connecting to up-to-date servers, without breaking compatibility with older ones.
HttpPost post = new HttpPost(Url); responsible for get POST request and send response.
HttpResponse response = client.execute(post); responsible for executes HTTP request using the default context.
HttpEntity entity = response.getEntity(); responsible for carry a content entity associated with the request or response.
For more information go to:http://hc.apache.org/httpcomponents-client-ga/tutorial/html/fundamentals.html

Android DefaultHttpClient Session Check

I'm very new to Android programming and I have following doubt.
I use DefaultHttpClient for making Http calls to my server. It works fine.
Are there any way to check whether the session is still live on my DefaultHttpClient object?
Is that possible to do so?
Thanks in advance.

Android persistent HttpClient connection

Would it be possible to setup an HttpClient such that on a website that updates periodically, perhaps due to AJAX, the resulting changes would be captured by the HttpClient. Similar to keeping a connection to a website alive, and if there were an update, the HttpClient would send the updated response to a listener of some type. I feel as if there is an obvious answer to my question, but I just haven't found it because I may have some of my terminology wrong...
This is just an example snippet of how I usually set up a connection:
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = httpClient.execute(httpGet);

Welcome to Stack Overflow! I do not think keeping a constant connection open to your site would be the best solution. Why don't you just poll every once in awhile?

Android DefaultHttpClient accept all certificates for SSL session help

I am attempting to connect to a local HTTPS server using the apache DefaultHttpClient on a Android device.
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://192.168.1.121:4113/services");
... header and content filling in ...
HttpResponse response = httpclient.execute(httppost);
I am getting an error of "javax.net.ssl SSLException: Not trusted server certificate" when the .execute runs. I want to simply allow any certificate to work, regardless of if it is or is not in the android key chain.
I have spent about 40 hours researching and trying to figure out a workaround for this issue. I have seen many examples of how to do this but none so far have worked in Android; they seem to only work for JAVA. Does anyone know how to configure, or override the certificate validation used by the Apache HttpClient in Android so that it will just approve all certificates for a DefaultHttpClient connection?
I thank you for your kind response

If anyone is still trying to figure this out I ended up going with the solution here:
HTTPS GET (SSL) with Android and self-signed server certificate
Scroll down to the solution by SimonJ. It is a simple straight forward solution to this problem.

Look at this tutorial http://blog.antoine.li/index.php/2010/10/android-trusting-ssl-certificates/
The tutorial is based on Apache's HttpClient and explains how to use the SSLSocketFactory to trust the defined certificates in your own keystore (also explained how you can create it with the BouncyCastle provider).
I've tested it and it works great. In my opinion this is the secure way.

how do i do authentification on android

I need to authenticate to use a rest web service.
I make a
HttpClient httpclient = new DefaultHttpClient();
an there must be a way to use UsernamePasswordCredentials on that client.
Can somebody please point me to a relevant example?
I have found some source code uding the HttpClient class in the org.apache.commons.SOMETHING_HTTP, but that doesn't exist on Android.
Cheers

This may help you : http://lukencode.com/2010/04/27/calling-web-services-in-android-using-httpclient/