Socket Programming in Java to send and receive byte array

Question

Am new to android and i have an issue with socket programming.

class ClientAsycTask extends AsyncTask<String,Void,String>{
    ProgressDialog progress;
    @Override
    protected void onPreExecute() {
        progress = new ProgressDialog(MainActivity.this);
        progress.setMessage("Connection Server Please wait");
        progress.setIndeterminate(true);
        progress.show();
    }

    @Override
    protected String doInBackground(String... params) {
        String result = null;
        Socket socket = new Socket();
        String host = "systemteq.gotdns.com";
        Integer port = 4999;
        DataOutputStream s_out = null;
        BufferedReader s_in = null;
        try{
            socket.connect(new InetSocketAddress(host, port));
            s_out = new DataOutputStream( socket.getOutputStream());
            s_in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            byte[] messages = new byte[]{0x10,0x01,0x03,0x00,0x00};
            s_out.write(messages);
            String response;
            while((response = s_in.readLine())!=null){
                result += response;
            }
            //result = "Successfully"+s_in.read();//s_in.readLine();
            socket.close();

        }catch (Exception e){
            Toast.makeText(MainActivity.this,"systemteq.gotdns.com:4999 not connected",Toast.LENGTH_SHORT).show();
        }
        return result;
    }

    @Override
    protected void onPostExecute(String s) {
        if(progress.isShowing()){
            progress.dismiss();
        }
        Toast.makeText(MainActivity.this,"Connected "+s,Toast.LENGTH_SHORT).show();
        tv.setText(s);
    }
}

Above code sends a hexadecimal code to server and server responds with some hexadecimal code, lets say 10 01 20 10 00.[five bytes].

But when i run above code progress dialog never close. after working around i found that s_in.readLine() has some issue reading the response from server.

I have went through lots of links but i was not successful while solving this issue. Kindly help me to crack this.

UPDATE:-

After using DataInputStream:-

s_in = new DataInputStream(socket.getInputStream());
            byte[] messages = new byte[]{0x10,0x01,0x03,0x00,0x00};
            s_out.write(messages);
            String response;
            System.out.println("START");
            result = s_in.readUTF();

It still does not take response byte. Though request is successful.

Update 2

byte m = s_in.readByte();
result = Byte.toString(m);

Now am getting byte value but i should get 5 bytes , instead of getting 5 bytes am getting only one. Please help me with this thing

Eugene Krivenja · Accepted Answer · 2016-04-08 14:16:13Z

3

If you are waiting for binary data, do not use InputStreamReader, try DataInputStream instead.
The readLine() waits for '\n', '\r', "\r\n" or the end of the reader.

UPDATE: if you know exact number of bytes, read them into array.

byte[] buf = new byte[5];
s_in.read(buf);

edited Apr 8, 2016 at 14:16

answered Apr 7, 2016 at 14:32

Eugene Krivenja

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4 Comments

Eugene Krivenja Over a year ago

If the server sends you bytes, why you trying always read them as String? Read bytes to byte[] buffer. It is easy. Strings are more complicated.

RKD Over a year ago

Hai @Eugene Krivenja thanks, this works fine now but now it is taking only one byte at a time. as i know it will return 5 bytes. do you have any idea

user207421 Over a year ago

@RKD No, readUTF() does not do the same thing as readLine(), as the most cursory glance at the documentation will show.

RKD Over a year ago

hi @EJP thanx , actually my response when i use readByte is 24 when i convert this to hex it is 18 which is then first byte of the response. Response is 18 06 05 00 00. Can you just tell me how can i take all this byte

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