Q: failed to connect to port 80 After clicking on login button "attempting to login" message is displayed only and no further activity is there in the app and also after clicking the button an exception is displayed in LOGCAT "java.net.ConnectException: failed to connect to /127.0.0.1 (port 80) after 15000ms: isConnected failed: ECONNREFUSED (Connection refused)" .May be only preexecute is running and not the background tasks.But Where is the problem ?
Login.java--->
public class Login extends Activity {
        AutoCompleteTextView UsernameEt;
        EditText PasswordEt;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_login);
            UsernameEt = (AutoCompleteTextView) findViewById(R.id.email);
            PasswordEt = (EditText) findViewById(R.id.password);
        }

        class PostAsync extends AsyncTask<String, String, JSONObject> {
            JSONParser jsonParser = new JSONParser();

            private ProgressDialog pDialog;

           // private static final String LOGIN_URL = "http://10.0.3.2:8080/login3.php";
           // private static final String LOGIN_URL = "http://192.168.*.*/login3.php";
           private static final String LOGIN_URL = "http://127.0.0.1/login3.php";

            private static final String TAG_SUCCESS = "success";
            private static final String TAG_MESSAGE = "message";


            @Override
            protected void onPreExecute() {
                pDialog = new ProgressDialog(Login.this);
                pDialog.setMessage("Attempting login...");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(true);
                pDialog.show();
            }

            @Override
            protected JSONObject doInBackground(String... args) {

                try {

                    HashMap<String, String> params = new HashMap<>();
                    params.put("name", args[0]);
                    params.put("password", args[1]);

                    Log.d("request", "starting");

                    JSONObject json = jsonParser.makeHttpRequest(
                            LOGIN_URL, "POST", params);

                    if (json != null) {
                        Log.d("JSON result", json.toString());

                        return json;
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }

                return null;
            }

            protected void onPostExecute(JSONObject json) {

                int success = 0;
                String message = "";

                if (pDialog != null && pDialog.isShowing()) {
                    pDialog.dismiss();
                }

                if (json != null) {
                    Toast.makeText(Login.this, json.toString(),
                            Toast.LENGTH_LONG).show();

                    try {
                        success = json.getInt(TAG_SUCCESS);
                        message = json.getString(TAG_MESSAGE);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }

                if (success == 1) {
                    Log.d("Success!", message);
                }else{
                    Log.d("Failure", message);
                }
            }

        }

        public void OnLogin(View view) {
            String username = UsernameEt.getText().toString();
            String password = PasswordEt.getText().toString();

            new PostAsync().execute(username, password);

        }
    }

................................................................................
JsonParser.java---->
public class JSONParser {

    String charset = "UTF-8";
    HttpURLConnection conn;
    DataOutputStream wr;
    StringBuilder result;
    URL urlObj;
    JSONObject jObj = null;
    StringBuilder sbParams;
    String paramsString;

    public JSONObject makeHttpRequest(String url, String method,
                                      HashMap<String, String> params) {

        sbParams = new StringBuilder();
        int i = 0;
        for (String key : params.keySet()) {
            try {
                if (i != 0){
                    sbParams.append("&");
                }
                sbParams.append(key).append("=")
                        .append(URLEncoder.encode(params.get(key), charset));

            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            i++;
        }

        if (method.equals("POST")) {
            // request method is POST
            try {
                urlObj = new URL(url);

                conn = (HttpURLConnection) urlObj.openConnection();

                conn.setDoOutput(true);

                conn.setRequestMethod("POST");

                conn.setRequestProperty("Accept-Charset", charset);

                conn.setReadTimeout(10000);
                conn.setConnectTimeout(15000);

                conn.connect();

                paramsString = sbParams.toString();

                wr = new DataOutputStream(conn.getOutputStream());
                wr.writeBytes(paramsString);
                wr.flush();
                wr.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        else if(method.equals("GET")){
            // request method is GET

            if (sbParams.length() != 0) {
                url += "?" + sbParams.toString();
            }

            try {
                urlObj = new URL(url);

                conn = (HttpURLConnection) urlObj.openConnection();

                conn.setDoOutput(false);

                conn.setRequestMethod("GET");

                conn.setRequestProperty("Accept-Charset", charset);

                conn.setConnectTimeout(15000);

                conn.connect();

            } catch (IOException e) {
                e.printStackTrace();
            }

        }

        try {
            //Receive the response from the server
            InputStream in = new BufferedInputStream(conn.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            result = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }

            Log.d("JSON Parser", "result: " + result.toString());

        } catch (IOException e) {
            e.printStackTrace();
        }

        conn.disconnect();

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(result.toString());
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON Object
        return jObj;
    }
}

