How to communicate from android application to Patient monitoring System (PMS) in the form of packets by using Socket connection? - sockets

Question

We are having patient monitoring system which is Wi-Fi enabled. Here the requirement to establish a communication between android application and Patient Monitoring System (PMS) device using Socket connection and communication should be happen in the form of packets. Once initiate the request, it continuously sends the data over Socket, but I am unable to form the data in the form of packets. Please can anyone help to how to send data in the form of data packets?
The request format is given below.
Header field denotes the type of the operation that is to be performed.
Data payload field contains two fields Length and Actual Data bytes.
The Data length field indicates the number of bytes of data that
follow.
The Data Payload field is optional.
The header field is shown below :–
1st bit is direction of transfer. 0 – Read, 1 – Write.
The Command field (7 bits) specifies the command to be executed.
The Option1 field will give the information about the parameter
that is under consideration.
The Option2 (lower 4 bits) and Option3 (upper 4 bits) fields
are optional. For certain commands, they carry data with specific
meaning. For certain other commands, they are just ignored.
Commands standards given below:-
Code snippet given below
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#2D3238"
android:padding="10dp">
<Button
android:id="#+id/connectBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginTop="10dp"
android:onClick="onClick"
android:text="Connect" />
</RelativeLayout>
MainActivity.java
package com.test.pms.app;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.test.pms.app.R;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
public class MainActivity extends Activity implements View.OnClickListener {
private Button connectBtn;
private Socket socket = null;
private boolean isRunning = false;
private String ipAddress = "192.168.1.55";
private int portNumber = 4561;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
connectBtn = (Button) findViewById(R.id.connectBtn);
}
#Override
protected void onResume() {
super.onResume();
isRunning = true;
}
#Override
protected void onPause() {
isRunning = false;
super.onPause();
}
#Override
public void onClick(View v) {
int id = v.getId();
switch (id) {
case R.id.connectBtn:
new CommunicateTask().execute();
break;
}
}
private class CommunicateTask extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
sendData();
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
}
}
private void sendData() {
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
try {
socket = new Socket(ipAddress, portNumber);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
MainActivity.this.runOnUiThread(new Runnable() {
#Override
public void run() {
connectBtn.setText(getString(R.string.connected));
}
});
/* byte[] byteArray = new byte[5];
byteArray[0] = (byte) 1; //direction 0-write and 1- read
byteArray[1] = (byte) 3; // Command Type 3 - CMD_TIMESTAMP
byteArray[2] = (byte) 1; //Option1- SPO2
byteArray[3] = (byte) 0; //Option2: Nothing
byteArray[4] = (byte) 1; //Option3 : RED*/
String command = "CMD_TIMESTAMP";
// byte arr[] = {1, 0, 0, 0, 0, 1, 0, 0};
dataOutputStream.writeUTF(command);
dataInputStream = new DataInputStream(socket.getInputStream());
//dataOutputStream.write(byteArray);
//dataOutputStream.writeUTF(command);
// dataInputStream.write(arr);
// dataOutputStream.writeUTF("Hello Server");
while (isRunning) {
if (socket.isConnected()) {
String b = dataInputStream.readLine();
}
}
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
#Override
protected void onDestroy() {
super.onDestroy();
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Here Socket connection is established successfully , but when I try read data from inputStream unable to read. Execution stopped at dataInputStream.readLine();.
I tried multiple methods to read data from InputStream like
dataInputStream.readLine();
dataInputStream.readByte();
dataInputStream.read();
Please can anyone help me to form request format in the form of packets and read the data in packets?
Thanks in advance.

Answer 1

This is an example on how to set each byte of the header.
To form the header, you can set each byte using hex numbers.
For example:
byte b = 0xA8;
A == 10 == 0011
8 == 8 == 1000
then b = A8 = 00111000;
Example:
Dir: 1
Command: 1010101 (just invented a command)
First byte is 11010101
We separate in two sets of four bits: 1101 0101
Thse binaries reperesent 13 5 in decimal and D 5 in hex
The first byte value for this command is 0xD5