CODEWITHSUNDEEP
androidmultithreadingsockets
Lance Lefebure
Lance Lefebure

Reputation: 6845

How to get data to/from a socket in a thread?

Android noob here. I learn the best by seeing the source code of a functional example, but I have been unable to find a simple-but-complete example of using a socket in its own thread.

I have an Android service that needs to communicate with the Internet. I want to open a TCP socket that connects to a server on the Internet. The service needs to send data to the Internet, and data coming back from the net will need to go to the service. Since the service is doing other things as well, the socket connection needs to live in its own thread.

Any idea where I could find an example of a socket in a thread with communication to/from the socket?

Thanks

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Upvotes: 9

Views: 30329

Answers (2)

Brian Griffey
Brian Griffey

Reputation: 4751

You simply need to create an async task that communicates in the background and then updates the UI thread as needed. Here is the background thread to get information from a socket and update a text view with the number of bytes it receivers

  public class InternetTask extends AsyncTask<Void, Integer, Void> {

    private WeakReference<TextView> mUpdateView;

    public LoginTask(TextView view) {
        this.mUpdateView = new WeakReference<TextView>(view);
    }

    @Override
    protected Void doInBackground() {

        try {
            Socket socket = new Socket("127.0.0.1", 80);
                    InputStream is = socket.getInputStream();

                    byte[] buffer = new byte[25];
                    int read = is.read(buffer);
                    while(read != -1){
                         publishProgress(read);
                         read = is.read(buffer);
                    }

                    is.close();
                    socket.close();



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

    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        if(mUpdateView.get() != null && values.length > 0){
                     mUpdateView.get().setText(values[0].toString());
                }
    }

}

And here is how you would kick that thread off

public class TestTab extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.someLayout);

            TextView textView = (TextView)findViewById(R.id.someid);
            InternetTask task = new InternetTask(textView);
            task.execute();

    }
}

Upvotes: 15

James Black
James Black

Reputation: 41858

Here is a long blog about this subject, where both the server and client parts are showing, with the socket communication going over a separate thread.

http://thinkandroid.wordpress.com/2010/03/27/incorporating-socket-programming-into-your-applications/

One thing to be aware of is that if you are passing ints you may run into a byte-order problem, so, just do some testing and I would suggest you ensure that the server sends in the format that the Android needs, in case you have servers on more than one OS.

For a simple way, on the Android to find the byte order you can use this: http://developer.android.com/reference/java/nio/ByteOrder.html

According to this article, byte order may be swapped for optimization: http://en.wikipedia.org/wiki/Dalvik_(software)

Upvotes: 8

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