The server socket helps you to connect the clients with server. In this tutorial we are going to build a message delivering application in android using server socket in which you could connect multiple clients(android devices) to the server(PC).
Steps:
1. Create a java project and add the following classes
server.java
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
public static void main(String args[]){
Socket s=null;
ServerSocket ss2=null;
System.out.println("Server Listening......");
try{
ss2 = new ServerSocket(4444); // can also use static final PORT_NUM , when defined
}
catch(IOException e){
e.printStackTrace();
System.out.println("Server error");
}
while(true){
try{
s= ss2.accept();
System.out.println("connection Established");
Reciever st=new Reciever(s);
st.start();
}
catch(Exception e){
e.printStackTrace();
System.out.println("Connection Error");
}
}
}
}//class ends
Sender.java
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
public class Sender {
private PrintWriter out;
public Sender(Socket clientSocket) {
try {
out = new PrintWriter(clientSocket.getOutputStream(), true);
} catch (IOException e) {
e.printStackTrace();
}
}
public void sendMessage(String message) {
out.println(message); // Print the message on output stream.
out.flush();
message="";
System.out.println("Server: " + message + "\n"); // Print the message on chat window.
}
}
Receiver.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
class Reciever extends Thread{
String line=null;
BufferedReader is = null;
PrintWriter os=null;
Socket s=null;
public Reciever(Socket s){
this.s=s;
}
public void run() {
try{
is= new BufferedReader(new InputStreamReader(s.getInputStream()));
os=new PrintWriter(s.getOutputStream());
}catch(IOException e){
System.out.println("IO error in server thread");
}
try {
line=is.readLine();
while(line.compareTo("QUIT")!=0){
os.println(line);
os.flush();
if(line.equals("syncDb")){
DataHandler a = new DataHandler();
a.syncDb(s);
break;
}
else{
//
System.out.println("Response to Client : "+line);
line=is.readLine();
}
}
} catch (IOException e) {
line=this.getName(); //reused String line for getting thread name
System.out.println("IO Error/ Client "+line+" terminated abruptly");
}
catch(NullPointerException e){
line=this.getName(); //reused String line for getting thread name
System.out.println("Client "+line+" Closed");
}
finally{
try{
System.out.println("Connection Closing..");
if (is!=null){
is.close();
System.out.println(" Socket Input Stream Closed");
}
if(os!=null){
os.close();
System.out.println("Socket Out Closed");
}
if (s!=null){
s.close();
System.out.println("Socket Closed");
}
}
catch(IOException ie){
System.out.println("Socket Close Error");
}
}//end finally
}
}
DataHandler.Java
import java.net.Socket;
public class DataHandler {
public static void syncDb(Socket s) {
Sender sender = new Sender(s);
sender.sendMessage("***start***");
sender.sendMessage("This is a message from the server");
sender.sendMessage("***stop***");
}
}
That's all for the server-side.
2.Copy and paste the below code to your android activity class.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends Activity {
private Socket client;
private PrintWriter printwriter;
private BufferedReader bufferedReader;
private ProgressDialog pDialog;
String host;
int port;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/**
* This AsyncTask create the connection with the server and initialize the
* chat senders and receivers.
*/
private class ChatOperator extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... arg0) {
try {
client = new Socket(host, port); // Creating the
// server socket.
if (client != null) {
printwriter = new PrintWriter(client.getOutputStream(),
true);
InputStreamReader inputStreamReader = new InputStreamReader(
client.getInputStream());
bufferedReader = new BufferedReader(inputStreamReader);
} else {
System.out
.println("Server has not bean started on port 4444.");
}
} catch (UnknownHostException e) {
System.out.println("Faild to connect server " + host);
e.printStackTrace();
} catch (IOException e) {
System.out.println("Faild to connect server " + host);
e.printStackTrace();
}
return null;
}
/**
* Following method is executed at the end of doInBackground method.
*/
@Override
protected void onPostExecute(Void result) {
final Sender messageSender = new Sender(); // Initialize chat sender
// AsyncTask.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
messageSender.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
messageSender.execute();
}
Receiver receiver = new Receiver(); // Initialize chat receiver
// AsyncTask.
receiver.execute();
}
}
/**
* This AsyncTask continuously reads the input buffer and show the chat
* message if a message is availble.
*/
private class Receiver extends AsyncTask<Void, Void, Void> {
private String message;
@Override
protected Void doInBackground(Void... params) {
while (true) {
try {
if (bufferedReader.ready()) {
message = bufferedReader.readLine();
publishProgress(null);
}
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
Thread.sleep(100);
} catch (InterruptedException ie) {
}
}
}
@Override
protected void onProgressUpdate(Void... values) {
try {
Toast.makeText(getApplicationContext(),
"Received message: "+message, Toast.LENGTH_LONG).show();
} catch (Exception e) {
// TODO: handle exception
}
}
}
/**
* This AsyncTask sends the chat message through the output stream.
*/
private class Sender extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
printwriter.write("message from client" + "\n");
printwriter.flush();
Log.d("message", "send");
return null;
}
@Override
protected void onPostExecute(Void result) {
}
}
public void LoadAndSave(View v) {
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Loading meassage. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
ChatOperator chatOperator = new ChatOperator();
chatOperator.execute();
}
}// activity ends
3. Copy and paste the below xml to you layout xml file.
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TableLayout
android:layout_width="fill_parent"
android:layout_height="172dp"
android:stretchColumns="1" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="20dp"
android:layout_marginTop="20dp"
android:onClick="LoadAndSave"
android:text="send a message to server" />
</TableLayout>
</ScrollView>
4.Finally add internet permission to your android manifest.
<uses-permission android:name="android.permission.INTERNET" >
Now run the server and connect as much as client!
