Question

So I’ve scoured the net (mostly SO, google) to find good examples of socket programming with Android. I’ve done lots of Android dev (just not with sockets). I dont understand why my readLine() ALWAYS RETURNS NULL. And please ignore the hideous code, this is a quick and dirty prototype for a friend. My overall goal is to establish a connection to a server, send header data (GET /MOUNTPOINT Content-Type: … etc…), and receive a response, based on the response I need to either continue the stream or close it. Here is my most recent attempts code:

                    String userPass = new     String(Base64.encodeToString("user:password".getBytes(),     Base64.DEFAULT));
            boolean connected = false;
            String requestmsg = "GET /MOUNTPOINT" + " HTTP/1.0\r\n";
            requestmsg += "User-Agent: MYCUSTOMAGENT\r\n";
            requestmsg += "Accept: */*\r\n";
            requestmsg += "Connection: close\r\n";

            requestmsg += "Authorization: Basic " + userPass;

            requestmsg += "\r\n";
            DataOutputStream dos =  null;
            DataInputStream dis = null;
            try {

                Log.d("ClientActivity", "Connecting...");
                Socket socket = new Socket("1.2.3.4", 9000);
                connected = true;
                String data = "";

                while (connected) {
                    try {
                        Log.d("ClientActivity", "C: Sending command.");

                        dos = new DataOutputStream(socket.getOutputStream());
                        dis = new DataInputStream(socket.getInputStream());

                        dos.write(requestmsg.getBytes());
                        Log.i("ClientActivity", "RequestMsg Sent");

                        StringBuilder sb = new StringBuilder();

                        while ((data = dis.readLine()) != null)
                            {
                                sb.append(data);
                            }
                            Log.i("ClientActivity", "C: Sent.");
                    } catch (Exception e) {
                        Log.e("ClientActivity", "S: Error", e);

                    }
                }
                socket.close();
                Log.d("ClientActivity", "C: Closed.");
            } catch (Exception e) {
                Log.e("ClientActivity", "C: Error", e);
                connected = false;
            }

I’ve tried using the HttpClient API but it inserts a “GET /” message in the header and I need to specify “GET /MOUNTPOINT”. Plus I don’t know if HttpClient allows streaming. Ive also tried URLConnection, but also it inserts either GET or POST by default. Thanks for any help!

Also I have tried the following:

SocketAddress sockaddr = new InetSocketAddress("1.2.3.4", 9000);
nsocket = new Socket();

nsocket.connect(sockaddr, 10 * 1000); // 10 second connection timeout
    if (nsocket.isConnected()) {
        //nsocket.setSoTimeout(20 * 1000); // 20 second timeout once data is flowing
        nis = nsocket.getInputStream();
        nos = nsocket.getOutputStream();
        Log.i(NTAG, "Socket created, streams assigned");
        // Build request message
        requestmsg = "GET /MOUNTPOINT" + " HTTP/1.0\r\n";
        requestmsg += "User-Agent: MYANDROIDAGENT\r\n";
        requestmsg += "Accept: */*\r\n";
        requestmsg += "Connection: close\r\n";
        requestmsg += "Authorization: Basic " + userPass;
        requestmsg += "\r\n";

        nos.write(requestmsg.getBytes());


        nos.write(genGPGGA().getBytes());
        Log.i(NTAG, "Waiting for inital data...");
        byte[] buffer = new byte[4096];
        int read = nis.read(buffer); // This is blocking
        //Log.i("ReadNTRIP", tempdata.toString());
        String test = "TESTING";

        while (read != -1) {
            tempdata = new byte[read];
            System.arraycopy(buffer, 0, tempdata, 0, read);
            read = nis.read(buffer, 0, 4096); // This is blocking

        }
    }
} catch (SocketTimeoutException ex) {
    ex.printStackTrace();
} catch (Exception e) {
    e.printStackTrace();
} finally {
    try {
        nis.close();
        nos.close();
        nsocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
    Log.i(NTAG, "Finished");

}

But read always returns -1. Im ready to pull my hair out.

EDIT: I added a bounty (worth very little) – I don’t have much rep to give, but this problem has become a show stopper for me. To get the bounty, write a simple android program to connect to thor.lsu.edu, port 9000, send a simple GET / HTTP/1.0 command and actually get back data (using sockets – cannot be with URLConnection or HttpClient). Post the program and a screenshot of the results. I’ve tried it so many different ways I don’t know what else to do (using InputStreams, BufferedInputStreams, InputStreamReaders, etc…). I’ve even used an example Android program (THAT WORKS), yet I still don’t get back data in my implementation. I don’t know if its a timing issue or what.

Thanks

Edit: I’ve noticed that I cannot even browse to http://thor.lsu.edu:9000 in Androids browser. It gives a data connectivity problem. Any idea why this port may be blocked?

Answer 1

All I did was a few modifications to your code. I think the major change was just not using the DataInputStream since the documentation explicitly says to not use readLine() anymore on this data structure. http://download.oracle.com/javase/1.4.2/docs/api/java/io/DataInputStream.html#readLine%28%29

I also remove the authorization stuff since it wasn’t required. If you run this code somewhere, you will notice the log printing out the HTTP response.

String requestmsg = "GET /MOUNTPOINT" + " HTTP/1.0\r\n";
    requestmsg += "User-Agent: MYCUSTOMAGENT\r\n";
    requestmsg += "Accept: */*\r\n";
    requestmsg += "Connection: close\r\n";

    // requestmsg += "Authorization: Basic " + userPass;

    requestmsg += "\r\n";
    DataOutputStream dos = null;
    BufferedReader dis = null;
    try {

        Log.d("ClientActivity", "Connecting...");
        Socket socket = new Socket("thor.lsu.edu", 9000);
        String data = "";

        try {
            Log.d("ClientActivity", "C: Sending command.");

            dos = new DataOutputStream(socket.getOutputStream());
            dis = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            dos.write(requestmsg.getBytes());
            Log.i("ClientActivity", "RequestMsg Sent");

            StringBuilder sb = new StringBuilder();

            while ((data = dis.readLine()) != null) {
                sb.append(data);
            }
            Log.i("ClientActivity", "C: Sent.");
            Log.i("ClientActivity", "C: Received " + sb.toString());
        } catch (Exception e) {
            Log.e("ClientActivity", "S: Error", e);

        }

        socket.close();
        Log.d("ClientActivity", "C: Closed.");
    } catch (Exception e) {
        Log.e("ClientActivity", "C: Error", e);
    }