Which URL to be used for app engine client in cloud computing?

I am using cloud computing in my app for push notification. I have a problem in client auth token. I am using the following for authenticating client login token

public class AppEngineClient {
    private static final String TAG = "AppEngineClient";

    public static final String BASE_URL = " <Don't know which URL to use here>";
    public static final String AUTH_URL = BASE_URL + "/_ah/login";
    public static final String AUTH_TOKEN_TYPE = "ah";

    public final Context mContext;
    public final String mAccountName;

    public AppEngineClient(Context context, String accountName) {
        this.mContext = context;
        this.mAccountName = accountName;
    }

    public HttpResponse makeRequest(String urlPath, List<NameValuePair> params) throws Exception {
        HttpResponse res = makeRequestNoRetry(urlPath, params, false);
        if (res.getStatusLine().getStatusCode() == 500) {
            res = makeRequestNoRetry(urlPath, params, true);
        }
        return res;
    }

    public HttpResponse makeRequestNoRetry(String urlPath, List<NameValuePair> params, boolean newToken)
            throws Exception {

        // Get auth token for account
        Account account = new Account(mAccountName, "com.google");
        String authToken = getAuthToken(mContext, account);
        if (authToken == null) throw new PendingAuthException(mAccountName);
        if (newToken) {  // invalidate the cached token
            AccountManager accountManager = AccountManager.get(mContext);
            accountManager.invalidateAuthToken(account.type, authToken);
            authToken = getAuthToken(mContext, account);
        }

        // Get ACSID cookie
        DefaultHttpClient client = new DefaultHttpClient();
        String continueURL = BASE_URL;
        URI uri = new URI(AUTH_URL + "?continue=" +
                URLEncoder.encode(continueURL, "UTF-8") +
                "&auth=" + authToken);
        HttpGet method = new HttpGet(uri);
        final HttpParams getParams = new BasicHttpParams();
        HttpClientParams.setRedirecting(getParams, false);  // continue is not used
        method.setParams(getParams);

        HttpResponse res = client.execute(method);
        Header[] headers = res.getHeaders("Set-Cookie");
        if (res.getStatusLine().getStatusCode() != 302 ||
                headers.length == 0) {
            return res;
        }

        String ascidCookie = null;
        for (Header header: headers) {
            if (header.getValue().indexOf("ACSID=") >=0) {
                // let's parse it
                String value = header.getValue();
                String[] pairs = value.split(";");
                ascidCookie = pairs[0];
            }
        }

        // Make POST request
        uri = new URI(BASE_URL + urlPath);
        HttpPost post = new HttpPost(uri);
        UrlEncodedFormEntity entity =
            new UrlEncodedFormEntity(params, "UTF-8");
        post.setEntity(entity);
        post.setHeader("Cookie", ascidCookie);
        post.setHeader("X-Same-Domain", "1");  // XSRF
        res = client.execute(post);
        return res;
    }

    public String getAuthToken(Context context, Account account) {
        String authToken = null;
        AccountManager accountManager = AccountManager.get(context);
        try {
            AccountManagerFuture<Bundle> future =
                    accountManager.getAuthToken (account, AUTH_TOKEN_TYPE, false, null, null);
            Bundle bundle = future.getResult();
            authToken = bund开发者_StackOverflow中文版le.getString(AccountManager.KEY_AUTHTOKEN);
            // User will be asked for "App Engine" permission.
            if (authToken == null) {
                // No auth token - will need to ask permission from user.
                Intent intent = new Intent("com.google.ctp.AUTH_PERMISSION");
                intent.putExtra("AccountManagerBundle", bundle);
                context.sendBroadcast(intent);
            }
        } catch (OperationCanceledException e) {
            Log.w(TAG, e.getMessage());
        } catch (AuthenticatorException e) {
            Log.w(TAG, e.getMessage());
        } catch (IOException e) {
            Log.w(TAG, e.getMessage());
        }
        return authToken;
    }

    public class PendingAuthException extends Exception {
        private static final long serialVersionUID = 1L;
        public PendingAuthException(String message) {
            super(message);
        }
    }
}

This is the class I am using for user authentication through app engine client through Chrome to phone example of cloud computing but I don't understand while using this class which BASE_URL, I have to give in this class. Please, tell me which URL to use and what to be done on server side if URL is from server side.

Thanks in advance

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The pattern for AppEngine base URLs is either

http://<<appname>>.appspot.com or https://<<appname>>.appspot.com