android - httpUrlConnection .connect() error crash -

in application code

@override     protected string doinbackground(void... params) {         stringbuilder response = null;         try {             string request = applicationconstants.request_about_base_uri;             url url = new url(request);             httpurlconnection conn = (httpurlconnection) url.openconnection();             conn.setrequestmethod("get");             conn.setreadtimeout(10000); // millis             conn.setconnecttimeout(15000); // millis             conn.connect();             log.d(tag, "doinbackground: " + conn.getresponsecode() + " : " + conn.getresponsemessage());             inputstream = conn.getinputstream();             bufferedreader rd = new bufferedreader(new inputstreamreader(is));             string line;             response = new stringbuilder();             while((line = rd.readline()) != null) {                 response.append(line);             }             rd.close();             log.d(tag, "doinbackground: " + response.tostring());         } catch (exception e) {             e.printstacktrace();         }         return response.tostring();     } 

crash error

http://pastebin.com/g6bxdfjj

unable resolve host "tools.mysite.com" in app constants request_about_base_uri write tools.mysyte.com/mobile.php?about

only real device , android 4.+. on android 5.0 .connect() ok.

why?