Server sent events in Android

Question

I have a backend server that sends events to clients as Server Sent Events. I haven't been able to find a good library for handling this technology on Android, so I've been using a fallback method of periodically checking the server (via a GET to an events endpoint) for new events.

This is done by a background service every 10 seconds. Needless to say, it's not the best approach. If there aren't any open source libraries already available for this scenario, what is the best approach in terms of memory usage and battery consumption to periodically check a server backend for new events? Is doing a GET to an API end point better or worse than managing an open socket in Android?

I'm open to any suggestions. Thanks.

Answer 1

You can simply use HttpUrlConnection to make a persistent connection with the server (Android uses keep-alive by default) and treat the received messages as streams.

public class HttpRequest extends AsyncTask {
    @Override
    protected Object doInBackground(Object[] params){
        try {
            URL url = new URL("http://simpl.info/eventsource/index.php");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            Log.d("SSE", "http response: " + urlConnection.getResponseCode());

            //Object inputStream = urlConnection.getContent();
            InputStream inputStream = new BufferedInputStream(urlConnection.getInputStream());
            Log.d("SSE reading stream", readStrem(inputStream)+"");
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            Log.e("SSE activity", "Error on url openConnection: "+e.getMessage());
            e.printStackTrace();
        }

        return null;
    }
}

private String readStrem(InputStream inputStream) {
    BufferedReader reader = null;
    StringBuffer response = new StringBuffer();
    try{
        reader = new BufferedReader(new InputStreamReader(inputStream));
        String line = "";
        while((line = reader.readLine()) != null){
            Log.d("ServerSentEvents", "SSE event: "+line);
        }
    }catch (IOException e){
        e.printStackTrace();
    }finally {
        if(reader != null){
            try{
                reader.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }
    return response.toString();
}