Unit – 3

Scripting

Q1) What is JavaScript?

A1) JavaScript

JavaScript is a dynamic programming language for computers. It is a lightweight component of web pages whose implementations allow client-side scripts to communicate with users and create dynamic pages. It's an object-oriented programming language that can be interpreted.

JavaScript is a lightweight, cross-platform object-based scripting language.

JavaScript is a translated language, not a compiled language. The JavaScript Translator (which is built into the browser) is in charge of translating JavaScript code for web browsers.

JavaScript (js) is a lightweight object-oriented programming language that is used to script webpages by a number of websites. When applied to an HTML document, it is an interpreted, full-featured programming language that enables dynamic interactivity on websites.

It was first released in 1995 to enable users to add programs to webpages in the Netscape Navigator browser. Since then, all other graphical web browsers have followed it. Users can use JavaScript to create modern web applications that communicate directly without having to reload the page every time. Js is used on a typical website to include various ways of interactivity and simplicity.

Q2) Write short notes on function and object?

A2) Function

A JavaScript function is a piece of code that performs a specific task.

When "something" calls a JavaScript method, it is executed (calls it).

The function keyword is used to describe a JavaScript function, which is then followed by a name and parentheses ().

Letters, numbers, underscores, and dollar signs can all be used in function names (same rules as variables).

Parameter names separated by commas can be used in the parentheses: (parameter1, parameter2, ...)

The function's code to be executed is enclosed in curly brackets: {}

function name(parameter1, parameter2, parameter3) {

  // code to be executed

}

Objects

A JavaScript object is a state and behavior-based entity (properties and method). For example, a car, a pen, a bicycle, a chair, a bottle, a keyboard, and a monitor.

JavaScript is an object-oriented programming language. In JavaScript, everything is an entity.

JavaScript is a template-based language, not a class-based language. To get the object, we don't need to build a class. However, we guide the creation of things.

Creating objects

Objects can be made in three different ways.

The following is the syntax for constructing an object with an object literal:

object={property1:value1,property 2:value2.....propertyN:valueN}

The syntax for explicitly constructing an object is as follows:

var objectname=new Object();

You must construct a function with arguments in this case. This keyword can be used to assign each argument value to the current object.

The current object is referred to by this keyword.

Q3) Give the Introduction to AJAX?

A3) Introduction to AJAX

The acronym Ajax stands for Asynchronous JavaScript and XML. It's used to connect with the server without having to refresh the tab, resulting in a better user experience and efficiency.

It's a set of technologies that work together, such as JavaScript, DOM, XML, HTML/XHTML, CSS, and XMLHttpRequest.

You can use AJAX to send and receive data asynchronously without having to reload the tab. As a result, it is fast.

You may use AJAX to send only the most relevant information to the server, rather than the whole page. As a result, only the most important data from the client is sent to the server. It improves the interactivity and speed of your application.

Yahoo, Facebook, Twitter, Google Maps, and YouTube are only a few examples of web applications that use ajax technology.

AJAX is a web-based application that employs a mixture of:

Fig 1: working of AJAX

Q4) What do you mean by internet addressing?

A4) Internet Addressing

An IP stands for internet protocol. An IP address is assigned to each device connected to a network. Each device uses an IP address for communication. It also behaves as an identifier as this address is used to identify the device on a network. It defines the technical format of the packets. Mainly, both the networks, i.e., IP and TCP, are combined together, so together, they are referred to as TCP/IP. It creates a virtual connection between the source and the destination.

We can also define an IP address as a numeric address assigned to each device on a network. An IP address is assigned to each device so that the device on a network can be identified uniquely. To facilitate the routing of packets, TCP/IP protocol uses a 32-bit logical address known as IPv4(Internet Protocol version 4).

Function:

The internet protocol's main purpose is to provide hosts with addresses, encapsulate data into packet structures, and route data from source to destination through one or more IP networks. The internet protocol provides two main items in order to achieve these functionalities, which are mentioned below.

●      Format of IP packet

●      IP Addressing system

IP packet

Until an IP packet is sent over the network, it contains two main components: a header and a payload.

Fig 2: IP packet

An IP header provides a lot of details about the IP packet, such as:

●      The source IP address is that of the person who is sending the data.

●      IP address of the destination: The destination is a host that collects data from the sender.

●      Header length

●      Packet length

●      TTL (Time to Live) of a packet is the amount of hops that must occur before the packet is discarded.

●      The internet protocol's transport protocol, which can be TCP or UDP, is known as the transport protocol.

The IP header contains a total of 14 fields, one of which is optional.

The data to be transported is known as the payload.

Q5) Explain InetAddress?

A5) InetAddress

Both the numerical IP address and the domain name for that address are encapsulated in the InetAddress class. This class is interacted with by using an IP host's name, which is more convenient and understandable than its IP address. The number is hidden within the InetAddress class. Both IPv4 and IPv6 addresses are supported by InetAddress.

The java.net framework. The IP address is encapsulated in Java's InetAddress class. Most other networking classes, such as Socket, ServerSocket, URL, DatagramSocket, DatagramPacket, and others, use it.

public final class InetAddress extends Object implements Serializable

This class has two fields that represent an Internet address: hostName (a String) and address (an int). The name of the host is included in hostName.

Creating New InetAddress Objects

The InetAddress class does not have any public constructors. InetAddress, on the other hand, has three static methods that, given a little detail, return appropriately initialized InetAddress items. They are as follows:

public static InetAddress InetAddress.getByName(String hostName)

 throws UnknownHostException

public static InetAddress[] InetAddress.getAllByName(String hostName)

 throws UnknownHostException

public static InetAddress InetAddress.getLocalHost()

 throws UnknownHostException

To fill out the information in the InetAddress object, all three of these may link to the local DNS server.

Q6) Define factory methods?

A6) Factory Methods

There are no visible constructors in the InetAddress class. You must use one of the available factory methods to build an InetAddress object. Static methods in a class that return an instance of that class are known as factory methods. When having specific method names makes the results much simpler, this is achieved instead of overloading a constructor with different parameter lists. Here are three widely used InetAddress factory methods:

The InetAddress object that represents the local host is returned by the getLocalHost() process. For a host name passed to it, the getByName() method returns an InetAddress.

On the Internet, it's popular to see a single name representing several machines. This is one way to have a degree of scaling in the world of web servers. The factory method getAllByName() returns an array of InetAddresses that represents all of the addresses that a given name resolves to. If it can't resolve the name to at least one address, it'll throw an UnknownHostException.

The factory method getByAddress(), which takes an IP address and returns an InetAddress object, is also included in InetAddress. You can use either an IPv4 or IPv6 address.

The addresses and names of the local computer, as well as two Internet web pages.

// Demonstrate InetAddress.

import java.net.*;

class InetAddressTest

{

public static void main(String args[]) throws UnknownHostException {

InetAddress Address = InetAddress.getLocalHost();

System.out.println(Address);

Address = InetAddress.getByName("www.HerbSchildt.com");

System.out.println(Address);

InetAddress SW[] = InetAddress.getAllByName("www.nba.com"); for (int i=0; i<SW.length; i++)

System.out.println(SW[i]);

}

}

This program's performance can be shown below. (Of course, the results you see can vary slightly.)

default/166.203.115.212

www.HerbSchildt.com/216.92.65.4

www.nba.com/216.66.31.161

www.nba.com/216.66.31.179

Q7) Describe instance methods?

A7) Instance Methods

There are some other methods in the InetAddress class that can be used on the objects returned by the methods. Here are a few of the most common methods:

boolean equals(Object other) : Returns true if this object has the same Internet address as other.

byte[ ] getAddress( ) : Returns a byte array that represents the object’s IP address in network byte order.

String getHostAddress() : Returns a string that represents the host address associated with the InetAddress object.

String getHostName() : Returns a string that represents the host name associated with the InetAddress object.

boolean isMulticastAddress() : Returns true if this address is a multicast address. Otherwise, it returns false.

String toString() : Returns a string that lists the host name and the IP address for convenience.

Fig 3: methods

A sequence of hierarchically cached servers is used to look up Internet addresses. That means your local computer can automatically recognize a specific name-to-IP-address mapping, such as for itself and nearby servers. It can ask a local DNS server for IP address information for other names. If that server doesn't have a specific address, it may request one from a remote location. This procedure can be followed all the way to the root server.

Q8) Explain TCP/IP Client Sockets?

A8) TCP/IP Client Sockets

A TCP/IP client socket connects two computers on a network in a secure, bi-directional, stream-based link. An instance of the Socket class is used to implement the client socket. Its aim is to establish a connection to the server and initiate protocol exchanges.

TCP/IP sockets are used to create stable, bidirectional, permanent, point-to-point, stream-based connections between Internet hosts. A socket connects Java's I/O device to other programs running on the local computer or on some other machine connected to the Internet.

In Java, there are two types of TCP sockets. The first is for servers, and the second is for clients. The ServerSocket class is intended to function as a "listener," meaning it will wait for clients to communicate before proceeding. As a result, ServerSocket is only for servers. Clients use the Socket class. Its purpose is to establish connections to server sockets and initiate protocol exchanges.

Methods to Create TCP Client Sockets

These methods can be used to build a Socket class object:

●      By using the following hostname and port number:

Socket (String hostname1, int port1)

Where hostname1 is a string style variable referring to the destination address, and port1 is the destination address's port number. In the event of an error, this method will throw the UnknownHostException or IOException exceptions.

●      By using the following syntax to define an InetAddress object and a port number:

Socket(InetAddress ipaddr1, int port1)

Where ipaddr1 is an item of the InetAddress class, and port1 is the destination's port number. In the event of an error, this method will throw the IOException exception.

Method of the Socket Class

InetAddress getInetAddress() -- Returns the InetAddress that is associated with the socket object.

int getPort() -- Returns the port number on which the socket is connected

int getLocalPort() -- Returns the local port number on which the socket is created

InputStream getInputStream() -- Returns the InputStream associated with the calling object.

OutputStream getOutputStream() -- Returns the OutputStream associated with the calling object.

void close() -- Closes the InputStream() and OutputStream() of the socket.

Example: Client Side Code

import java.net.*;

import java.io.*;

class clientsock

{

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

 {

  System.out.println("sending request to server....");

  Socket client=new Socket("127.0.0.1",1235);

  System.out.println("successfully conneted");

  BufferedReader br1=new BufferedReader(new InputStreamReader(System.in));

  PrintStream ps=new PrintStream(client.getOutputStream());

  BufferedReader br=new BufferedReader(new InputStreamReader(client.getInputStream()));

  while(true)

  {

   System.out.println("input the data u want to send to echo server: ");

   String s=br1.readLine();

   ps.println(s);

   if(s.equals("exit"))

   {

    System.exit(1);

   } 

   String st=br.readLine();

   System.out.println("data returned by the server:   ");

   System.out.println(st);

  }

 }

}

Q9) Explain URL?

A9) URL, URL Connection

The Uniform Resource Locator (URL) is a format for specifying addresses on the World Wide Web. A URL is the most basic network identifier for any resource on the internet (e.g., hypertext pages, images, and sound files).

The URL is a relatively comprehensible format for identifying or addressing information on the Internet. URLs are everywhere; they're used by every browser to find information on the Internet. The URL class in Java's network class library provides an easy, succinct API for accessing information over the Internet via URLs.

An URL is represented by the Java URL class. Uniform Resource Locator is an acronym for Uniform Resource Locator. It directs you to a World Wide Web resource.

Constructor of java URL Class

URL (string spec)

From the String representation, creates an instance of a URL.

URL (String protocol, String host, int port, String file)

From the specified protocol, host, port number, and file, creates an instance of a URL.

URL (String protocol, String host, int port, String file, URLStreamHandler handler)

Creates a URL from the protocol, host, port number, file, and handler arguments.

URL (String protocol, String host, String file)

From the specified protocol name, host name, and file name, creates an instance of a URL.

URL (URL context, String spec)

By parsing the given spec within a given context, this method creates an instance of a URL.

URL (URL context, String spec, URLStreamHandler handler)

By parsing the given spec with the specified handler within a given context, this method creates an instance of a URL.

Q10) What is URL Connection?

A10) URL Connection

A communication link between the URL and the application is represented by the Java URLConnection class. This class can be used to read and write data to the URL-referenced resource defined.

An active link to a resource defined by a URL is represented by the abstract class URLConnection. The URLConnection class serves two distinct but complementary purposes. For starters, it gives you more control over how you communicate with a server than the URL class does. You may inspect the MIME headers sent by an HTTP server and react appropriately using a URLConnection.

The MIME header fields used in the client request may be modified. A URLConnection can be used to import binary files. Finally, a URLConnection allows you to use POST and PUT to send data back to a web server, as well as other HTTP request methods.

Second, like the URLStreamHandler class, the URLConnection class is part of Java's protocol handler mechanism. Protocol handlers have a basic concept: they distinguish the details of processing a protocol from the details of processing specific data types, providing user interfaces, and other tasks that a monolithic web browser performs. Java.net is the foundation.

The URLConnection class is abstract; you must create a subclass to enforce a particular protocol. These subclasses may be loaded at runtime by your own applications or the HotJava browser; in the future, Java applications will be able to download protocol handlers as required over the Internet, allowing them to be automatically extensible.

How to get the object of URLConnection class

The URL class's openConnection() method returns a URLConnection item. The syntax is as follows:

public URLConnection openConnection()throws IOException{}

Displaying source code of a webpage by URLConnecton class

Using the getInputStream() method of the URLConnection class, we may show all of the data from a webpage. The getInputStream() method returns all of the data in the stream that can be read and displayed for the given URL.

Example:

import java.io.*; 

import java.net.*; 

public class URLConnectionExample { 

public static void main(String[] args){ 

try{ 

URL url=new URL("http://www.javatpoint.com/java-tutorial"); 

URLConnection urlcon=url.openConnection(); 

InputStream stream=urlcon.getInputStream(); 

int i; 

while((i=stream.read())!=-1){ 

System.out.print((char)i); 

} 

}catch(Exception e){System.out.println(e);} 

} 

} 

Q11) Describe TCP/IP Server Sockets?

A11) TCP/IP Server Sockets

For server applications, Java has a separate socket class that must be used. The Server Socket class is used to build servers that listen on published ports for connections from local or remote client programs. Server Sockets are not the same as regular Sockets.

When you build a Server Socket, it will inform the device that it is interested in receiving client connections. Server Socket’s constructors represent the port number on which you want to accept connections and, optionally, the length of the queue for that port.

The queue length informs the machine how many pending client connections it will keep before simply rejecting them. The default is 50. Under certain circumstances, the constructors can throw an IOException.

Three of its constructors are as follows:

Fig 4:  constructor

Accept() is a blocking method on Server Socket that waits for a client to initiate communication before returning with a regular Socket that can be used to communicate with the client.

Q12) Explain datagram?

A12) Datagram

TCP/IP networking is suitable for the majority of networking requirements. It generates a stream of packet data that is serialized, predictable, and dependable. However, there is a price to pay for this. TCP requires a number of complex algorithms for congestion management on congested networks, as well as negative packet loss predictions. As a result, data is transported in an inefficient manner. Datagrams are a different choice.

Datagrams are information packets that are sent between computers. They resemble a hard throw to the third baseman from a well-trained yet blindfolded catcher.

There is no guarantee that the datagram will arrive at its intended destination or that anyone will be there to catch it after it has been posted. Similarly, there is no guarantee that the datagram was not destroyed in transit or that the person who sent it is still alive to receive an answer when it is received.

Java uses two groups to implement datagrams on top of the UDP protocol: the Datagram Packet object is the data container, and the Datagram Socket is the mechanism for sending and receiving Datagram Packets.

Datagram Socket

Datagram Socket defines four public constructors. They are shown here: DatagramSocket() throws SocketException

DatagramSocket(int port) throws SocketException

DatagramSocket(int port, InetAddress ipAddress) throws SocketException DatagramSocket(SocketAddress address) throws SocketException

The first creates a DatagramSocket on the local machine that is connected to any unused port. The second generates a DatagramSocket with port as its destination. The third creates a DatagramSocket with the required InetAddress and port. The fourth creates a

The required SocketAddress is bound to the DatagramSocket. The concrete class InetSocketAddress implements the abstract class SocketAddress. InetSocketAddress encapsulates a port number and an IP address. If an error occurs when making the socket, both of them may throw a SocketException.

Many methods are described by DatagramSocket. Send( ) and receive( ), two of the most common, are seen here:

void send(DatagramPacket packet) throws IOException void receive(DatagramPacket packet) throws IOException

Fig 5: other method of datagram socket

Q13) Write the application of scripting?

A13) Application of Scripting

Scripting languages are used in a variety of applications:

●      Online applications make use of scripting languages. It's used both on the server and on the client. JavaScript, PHP, Perl, and other server-side scripting languages are available, as are JavaScript, AJAX, and jQuery for client-side scripting.

●      In device management, scripting languages are used. Shell, Perl, and Python scripts, for example.

●      It's used in video games and multimedia.

●      It's used to make plugins and extensions for other programs.

Q14) Write the advantages of scripting?

A14) Advantages of Scripting

●      Easy learning - The consumer does not need much knowledge of web technology to learn to code in scripting languages.

●      Fast editing - With just a few data structures and variables to work with, it's extremely powerful.

●      Interactivity - It aids in the incorporation of visualization interfaces and variations into web pages. Scripting languages are needed for modern web pages. To make better web pages, use a visual explanation that includes background and foreground colors, among other things.

●      Functionality - There are several libraries that are used in various scripting languages. They vary from traditional programming languages in that they assist in the development of new applications in web browsers.

Q15) Write the disadvantages of scripting?

A15) Disadvantages of Scripting

●      It necessitates the installation of scripting tools on the server.

●      Databases are required by several scripts and CMS tools to store dynamic data.

●      Because of the existence of complex scripts, new security issues arise. In certain cases, exploiting code bugs makes it easier for hackers to gain access to servers.