Android Asynctask用于套接字扫描

Question

I am trying to figure out the best way to loop over all ips in a range(IE 192.168.5.0-192.168.5.255) to find devices that are listening on a given port. The following code is working but I am worried that I wont find all the devices since I have my timeout on my socket too low. The catch 22 is that I want this to be super fast but if I up the timeout it starts to take forever.

private class findNetworkDevices extends AsyncTask<String, Integer, String> {

    private String source;
    private Activity activity;
    private Context context;
    public findNetworkDevices(Activity activity) {
        this.activity = activity;
        context = activity;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        for (int dest = 0; dest < 255; dest++) {
            String host = "192.168.5." + dest; // TODO: add net address instead of hardcoding
            try {
                Socket s = new Socket();
                s.connect(new InetSocketAddress(InetAddress.getByName(host), 9999), 50);
                Log.v(LOG_TAG, "conn:" + s.toString());
                if (s.isConnected()) {
                    Log.v(LOG_TAG, "connected " + host);
                    foundDevicesArray.add(host);
                } else {
                    return "failed";
                }
            } catch (Exception e) {
                Log.e(LOG_TAG, "Not found", e);
            }
            }
            Log.v(LOG_TAG, "end");

            return "All Done!";
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            ListView lv = (ListView) activity.findViewById(R.id.foundDevicesList);
            ((BaseAdapter) lv.getAdapter()).notifyDataSetChanged();

        }
    }

Thanks in advance.

Answer 1

I went away from using Async because it took so long. I went with ExecutorService

        ExecutorService executor = Executors.newFixedThreadPool(NB_THREADS);
    String ip = getLocalIpAddress();
    int endIndex = ip.lastIndexOf(".");
    String subnet = ip.substring(0, endIndex);
    for (int dest = 0; dest < 255; dest++) {
        String host = subnet + "." + dest;
        executor.execute(pingRunnable(host));
    }

It seems to spawn multiple threads where Async did it in the background but only in one thread.