Why Web Services? (Intro)

Well, before we start WHY, let see WHAT is a web service...!

 According to Wikipedia, it's something like follows.

“A Web service is a method of communication between two electronic devices over World Wide Web. A web service is a software function provided at a network address over the web or the cloud; it is a service that is 'always on' as in the concept of utility computing “ - wikipedia (6 February 2014) - (http://en.wikipedia.org/wiki/Web_service) 

But, let me put this into bit more simple way..!

• Web services are application components which can be used by other applications and 
• Web services communicate using open protocols like HTTP.
• Web services are self-contained and self-describing.
• Web services can be discovered using UDDI (Universal Description & Discovery Integration).
• HTTP and XML is the basis for Web services.

Basically a web service is an application component which has been exposed to World Wide Web where other application can access and request for a particular service regardless the implemented language or deployed environment.

It's the common media which makes a service interoperable..!

Why an Interoperability a Priority ?? 

Different platforms couldn't or rather I say, hard to interact with each other which brings us to the next obstetrical. 

When it comes to distributed systems, integration technologies or simply integration among systems plays a major role in order to carry out one single, happy transaction or a task. 

Apparently the implementations of the systems in a distributed environment are different form one to another, making communication more and more complex.

May be the communication media of a system could be totally alien to the other systems briefly..! 

So the solution is pretty much clear or at least it seems it would..!

Moving toward a common media, so all the applications which are eligible to communicate over it, can access the same set of exposed data. 

World Wide Web or WWW can be access by all the major platforms via a web browser, which makes it a common media.

That's actually the origin of WEB APPLICATIONS..!

But apart from that, what about non major platforms? Are we going to omit them??

No way, because some new platforms are way more robust, unique, effective and remarkable than an existing major platforms...!

For an example, get WSO2 Identity Server which provides a role base, policy base access control and single sign on over conventional authentication and authorization management (such as Spring security) to an enterprise web application.

So the question is, how we going to utilize them??

Easy...! Expose them as web services to WWW, so any application which requires it's service can access and communicate, platform independently.

Taking WS to the next level..!

By using Web services, your application can publish its function or message to the rest of the world as I mentioned previously.

Web services use XML to code and to decode data, and SOAP to transport it..!

But trust me, there're some other ways like REST (REpresentational State Transfer), but we'll have a different session for that..!

Basically, usage of a web services can be speared down into two major categories..!

1. Reusable application-components.
2. Integrate existing software applications.

• Reusable application-components

There are common components which software applications need frequently. 

So why make these components over and over again?

Web services can offer common application-components like Currency conversion, Payment gateways, Weather reports, or even Language translation as services.

• Integrate existing software applications.

Web services can be helpful to solve an interoperability problems by linking different applications in different platforms which providing a way to communicate with each other.

If you're new to WS or integration technologies and looking for something to start, hope this helped. Thanks for reading this post and please leave a comment if you're having any doubts..!

Happy Hunting..!

Socket / Network programming

Why socket programming?

With the escalation of distributed computing, single software needs to communicate with Internet or devices (may be another computer) on a network in order to carry out a task.

Socket is one of the fundamental aspect in computing which allows to communicate over a network using standard mechanisms, such as stream communication protocols (TCP/IP), datagram communication protocols (UDP/IP). 

Where can I find socket in real life?

If you're reading this, that means you are consuming the precious advantages of socket programming.

Yes..Indeed, your browser works as a client to communicate with the Internet, which is end of the day, a software. In addition to that peer-to-peer file transfer programs, instant messaging services, remote device connectivity (pay your bills from debit or credit card) for transactions can be best examples.  

How socket applications work?

Nutshell, it’s more or less like getting a telephone call to one of your friend. Requires two parties and one acts as a client (caller) while the other as a server (receiver). In order to get a call, you need to know the specific number belongs to your receiver, which is like host and the port of the server end of the day in network programming.

If you know the exact host and the port which has been exposed to a certain service, you can establish a connection over TCP/IP or UDP/IP to communicate. In order to establish the connectivity, you need to declare a socket while the sever listening to exact same socket.

It’s like you’re dialling to your friends’ phone, you have to wait until your friend accepts the call. Once he/she does accepts your call, then stats the communication until one of you hang (cut the connection) the phone. Exact same principle applies for the sockets as well, once you established the connectivity, you’re good to communicate and once you’re done connection close.

Have a look on bellow figure (1.1) to get further understanding on client-server communication.

 

figure 1.1

TCP/IP or UDP/IP?

The base protocol of a socket implementation highly varies on the requirement. 

TCP/IP (Transfer Control Protocol) is a streaming protocol which allows you to perform multiple bidirectional communication without limitation, once opened the socket till the close operation.

But when it comes to datagram protocols like UDP/IP (User Datagram Protocol), it allows bidirectional communication but requires authentication token per every sprint. And also UDP/IP maintains data limits for communication at each sprint.

In general, if you want a quick response sprints or to implement your own security infrastructure, implementing sockets over UDP would be an ideal. But for commonly used interfaces or for services TCP plays a better roll but with proper security.

Socket Programming in JAVA

In Java java.net.Socket class implements the Socket class and as the listener (server) has been implemented at java.net.ServerSocket.  

Let’s code a simple client named ClientSocketImp.java as follows:

package com.manish.socket.client;

import java.net.*;

import java.io.*;

public class ClientSocketImpl {

    private static String reqMessage = "135.90";

    private static String host = "127.0.0.1";

    private static int port = 7892;

    private static Socket socket = null;

    private static ObjectOutputStream objectOutputStream = null;

    private static ObjectInputStream objectInputStream = null;

    public static void main(String[] args) throws UnknownHostException, IOException, ClassNotFoundException, InterruptedException {

        socket = new Socket(host, port);

        objectOutputStream = new ObjectOutputStream(socket.getOutputStream());

        System.out.println("ACQUIRING SERVER CONNECTIVITY....");

        objectOutputStream.writeObject(reqMessage);

        objectInputStream = new ObjectInputStream(socket.getInputStream());

        String message = (String) objectInputStream.readObject();

        System.out.println("RESPONSE : " + message);

        objectInputStream.close();

        objectOutputStream.close();

    }

}

Okay, one more tiny step..Let’s code a simple server named SocketServerImpl.java as follows.

package com.manish.socket.client;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.lang.ClassNotFoundException;

import java.net.ServerSocket;

import java.net.Socket;

import java.text.MessageFormat;

public class SocketServerExample {

    private static ServerSocket server;

    private static int port = 7892;

    private static String response;

    public static void main(String args[]) throws IOException, ClassNotFoundException {

        server = new ServerSocket(port);

        while(true) {

            System.out.println("WAITING FOR A CLIENT REQUEST...");

            Socket socket = server.accept();

            ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());

            String message = (String) ois.readObject();

            double value = 0.00;

            try {

               value = Double.parseDouble(message.trim());

               value += returnInterest(value);

               response = MessageFormat.format("Your interest + amount Rs {0}", value);

            } catch (NumberFormatException e) {

                response = "Invalid request";

                e.printStackTrace();

            }

            ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());

            oos.writeObject(response);

            ois.close();

            oos.close();

            socket.close();

            if(message.equals("-1")) {

                break;

            }

        }

        server.close();

    }

    private static Double returnInterest(Double amount) {

        if(amount < 10) {

            return ((amount/100)*5.2);

        } else if (amount < 50) {

            return ((amount/100)*8.1);

        } else if (amount < 100) {

            return ((amount/100)*10.3);

        } else {

            return ((amount/100)*12.5);

        }

    }

}

Okay..Now done...!

First run the server class and then the client. This is a very simple interest returning application, where a client can send an amount to server over a socket and get the interest added amount as the response.  

You can try this out by yourself and try to fetch something better out of it...! Enjoy and good luck..!