GitHub - melvin7/AndroidAsync: Asynchronous socket and http library for android. Based on nio, not threads. Seriously though, you probably don't need this. I wrote it for a Tethering app, where hundreds of threads waiting for data input would crush your phone. Your app won't have those demands.

AndroidAsync is a java.nio based socket and http library for Android.

It uses java.nio to manage connections. All the connections are thus managed on a single thread, rather than one per thread. NIO is extremely efficient.

Download a url to a String

// url is the URL to download. The callback will be invoked on the UI thread
// once the download is complete.
AsyncHttpClient.get(url, new AsyncHttpClient.StringCallback() {
    @Override
    // Callback is invoked with any exceptions/errors, and the result, if available.
    public void onCompleted(Exception e, String result) {
        if (e != null) {
            e.printStackTrace();
            return;
        }
        System.out.println("I got a string: " + result);
    }
});

Download a url to a file

AsyncHttpClient.get(url, filename, new AsyncHttpClient.FileCallback() {
    @Override
    public void onCompleted(Exception e, File result) {
        if (e != null) {
            e.printStackTrace();
            return;
        }
        System.out.println("my file is available at: " + result.getAbsolutePath());
    }
});

AndroidAsync also let's you create simple HTTP servers:

// listen on port 5000
AsyncHttpServer mServer = new AsyncHttpServer(5000);
mServer.get("/", new HttpServerRequestCallback() {
    @Override
    public void onRequest(AsyncHttpServerRequest request, AsyncHttpServerResponse response) {
        response.send("Hello!!!");
    }
});
// browsing http://localhost:5000 will return Hello!!!