Socket Programming

This is a sample program that uses socket class to make a chat application, by this you can create a Server and a Client in two Emulator and chat to write and read data.

Underlying Algorithm:

Basic description of algorithm in step by step form:
1.) Create Two Projects one for server MyServer and another for client ServerClient.
2.) Put the following code snippet in res folder of MyServer project res/layout/main.xml :

<?xml version=”1.0″ encoding=”utf-8″?>
<LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android”
android:orientation=”vertical”
android:layout_width=”fill_parent”
android:layout_height=”fill_parent”>
<TextView
android:layout_width=”fill_parent”
android:layout_height=”wrap_content”
android:text=”@string/hello”
/>
<TextView android:text=”TextView” android:id=”@+id/TextView01″android:layout_width=”wrap_content” android:layout_height=”wrap_content”>
</TextView>
</LinearLayout>

3.) Put the following code snippet in res folder of ServerClient project res/layout/main.xml :

<?xml version=”1.0″ encoding=”utf-8″?>
<LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android”
android:orientation=”vertical”
android:layout_width=”fill_parent”
android:layout_height=”fill_parent”>
<TextView
android:layout_width=”fill_parent”
android:layout_height=”wrap_content”
android:text=”@string/hello”
android:id=”@+id/myTextView”
/>
<EditText android:text=”EditText” android:layout_width=”fill_parent”android:id=”@+id/EditText01″ android:layout_height=”wrap_content”>
</EditText>
<Button android:text=”Button” android:id=”@+id/myButton”android:layout_width=”wrap_content” android:layout_height=”wrap_content”>
</Button>
</LinearLayout>

4.) Add the following permissions in AndroidManifest.xml of both project :

<uses-permission android:name=”android.permission.INTERNET”> </uses-permission>
<uses-permission android:name=”android.permission.ACCESS_NETWORK_STATE”> </uses-permission>

5.) Redirect the port :

i) run -> cmd -> telnet localhost 5554
ii) redir add tcp:5000:6000

6.) Run the both applications.

Steps to Create Server:

1.) Open Eclipse. Use the New Project Wizard and select Android Project Give the respective project name i.e. MyServer. Enter following information:
Project name: MyServer
Build Target: Android APIs 2.1
Application name: MyServer
Package name: com.app. MyServer
Create Activity: MyServer

On Clicking Finish MyServer code structure is generated with the necessary Android Packages being imported along with MyServer.java. MyServer class will look like following:

package com.app.MyServer; import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;public class MyServer extends Activity {
ServerSocket ss = null;
String mClientMsg = “”;
Thread myCommsThread = null;
protected static final int MSG_ID = 0×1337;
public static final int SERVERPORT = 6000;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView tv = (TextView) findViewById(R.id.TextView01);
tv.setText(“Nothing from client yet”);
this.myCommsThread = new Thread(new CommsThread());
this.myCommsThread.start();
}
@Override
protected void onStop() {
super.onStop();
try {
// make sure you close the socket upon exiting
ss.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Handler myUpdateHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_ID:
TextView tv = (TextView) findViewById(R.id.TextView01);
tv.setText(mClientMsg);
break;
default:
break;
}
super.handleMessage(msg);
}
};
class CommsThread implements Runnable {
public void run() {
Socket s = null;
try {
ss = new ServerSocket(SERVERPORT );
} catch (IOException e) {
e.printStackTrace();
}
while (!Thread.currentThread().isInterrupted()) {
Message m = new Message();
m.what = MSG_ID;
try {
if (s == null)
s = ss.accept();
BufferedReader input = new BufferedReader(newInputStreamReader(s.getInputStream()));
String st = null;
st = input.readLine();
mClientMsg = st;
myUpdateHandler.sendMessage(m);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}

Steps to Create Client:

2.) Open Eclipse. Use the New Project Wizard and select Android Project Give the respective project name i.e. ServerClient. Enter following information:
Project name: ServerClient
Build Target: Android APIs 2.1
Application name: ServerClient
Package name: com.app.ServerClient
Create Activity: ServerClient

On Clicking Finish ServerClient code structure is generated with the necessary Android Packages being imported along with ServerClient.java. ServerClient class will look like following:

package com.app.ServerClient; import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View;
public class SocketClient extends Activity {
private Button bt;
private TextView tv;
private Socket socket;
private String serverIpAddress = “10.0.2.2″;
// AND THAT’S MY DEV’T MACHINE WHERE PACKETS TO
// PORT 5000 GET REDIRECTED TO THE SERVER EMULATOR’S
// PORT 6000
private static final int REDIRECTED_SERVERPORT = 5000;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bt = (Button) findViewById(R.id.myButton);
tv = (TextView) findViewById(R.id.myTextView);
try {
InetAddress serverAddr = InetAddress.getByName(serverIpAddress);
socket = new Socket(serverAddr, REDIRECTED_SERVERPORT);
} catch (UnknownHostException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
bt.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
try {
EditText et = (EditText) findViewById(R.id.EditText01);
String str = et.getText().toString();
PrintWriter out = new PrintWriter(new BufferedWriter(newOutputStreamWriter(socket.getOutputStream())),true);
out.println(str);
Log.d(“Client”, “Client sent message”);
} catch (UnknownHostException e) {
tv.setText(“Error1″);
e.printStackTrace();
} catch (IOException e) {
tv.setText(“Error2″);
e.printStackTrace();
} catch (Exception e) {
tv.setText(“Error3″);
e.printStackTrace();
}
}
});
}
}

Output –The final output:
Client :

Server :

Thanks & Regards

akm(cdacians)

www.cdacians.com