'Check the metadata of the latest hosts data file from server and
show a status box indicating current operation.
:return: A dictionary containing the `Version`, `Release Date` of
current hosts data file and the `Latest Version` of the data file
on server.
IF error occurs while checking update, the dictionary would be
defined as::
{"version": "[Error]"}
:rtype: dict'

def check_update(self):

    self.messagebox('Checking    Update...')
    srv_id = self.settings[0][1]
    url = (self.settings[0][2][srv_id]['update'] + self.infofile)
    try:
        socket.setdefaulttimeout(5)
        url_obj = urllib.urlopen(url)
        j_str = url_obj.read()
        url_obj.close()
        info = json.loads(j_str)
    except:
        info = {'version': '[Error]'}
    self.hostsinfo['Latest'] = info['version']
    self.status()
    return info
