Difference between Core Java and Advanced Java

The main difference between Core Java and Advanced Java is that the Core Java is used to build general applications while the Advanced Java is used to build enterprise level applications. Java is a general-purpose high-level programming language that helps to build a variety of applications. Java is popular as it provides platform as it provides various features such as independency, [ [ ...]

Java Networking Classes and Interfaces

1. JAVA AND THE NET Java has some distinct advantages over other programming languages as far as network applications are concerned. One of the important features of Java is that it supports 16-bit Unicode for International character sets, which is still difficult to implement in other languages. In addition, Java can excellently handle network security [ [ ...]

Java Networking: URL

The primary classes to access the Internet are the java.net.URL class and the java.net. HttpURLConnection class. The class url encapsulates the Uniform Resource Locator (URL), which identifies a resource in the WWW uniquely. A resource can be anything such as a file or a directory, or it can be a reference to a more complicated [ [ ...]

Java Networking Proxy

1. PROXY To address security issue, network administrators often install a special component called “proxy server.” It is essentially a service that sits between the Internet and the internal network and manages connections between the two worlds. This way, proxies reduce outside security threats while still allowing internal users to access Internet services. However, Java [ [ ...]

Client/server Programs in Java

One of the central ideas of network computing is client-server model. Many networking applications including the Internet’s primary protocols such as HTTP, SMTP, DNS, etc. use this model. It has some distinct advantages over its counterpart, the peer-to-peer model (P2P) where peers are equally privileged, equipotent participants [Figure 13.2:]. Note that sockets may also be [ [ ...]

Sockets Programming in Java

A socket, in network terminology, is an end-point for communication between two processes on the network. In Java, sockets are represented by objects for exchanging data. The java.net package provides useful classes and interfaces for communication using sockets. Note that a socket is not a connection, it is an endpoint of communication. Sockets objects are [ [ ...]

TCP Sockets in Java

As mentioned earlier, Java TCP socket API supports Transmission Control Protocol (TCP). The java.net package provides ServerSocket and Socket classes to support TCP. To understand the functionality of these classes, let us first recapitulate TCP style of communication quickly. In this style of communication, a logical channel is created (using a three-way handshaking procedure) prior [ [ ...]

UDP Sockets in Java

In the previous sections, we have discussed how to develop network applications using stream sockets. Communication with a server using stream socket basically consists of two steps. First, create a channel with the server at the desired port. Then, send and receive data through this channel. The stream socket provides reliable communication of ordered stream [ [ ...]

Multicast Sockets in Java

1. MULTICASTING In all the programs that we have developed so far, the data is destined to only one target. In other words, the number of receivers in all those cases was only one. This type of communication is known as uni-cast. Though many applications use this style of communication, there are instances, where a [ [ ...]

Useful Methods of ServerSocket Class

The following sections give a summary of important methods of ServerSocket class. 1. Constructors ServerSocket() Creates a raw server socket which is not yet bound to a specific socket address (IP address and port). However, the binding may be done later using bind() method. ServerSocket(int port) Creates a server socket and bounds it to the [ [ ...]

Useful Methods of Socket Class

The following sections give a summary of important methods of Socket class. 1. Constructors Socket() Creates a raw socket which is not yet bound to a specific socket address (IP address and port). However, the binding may be done later using bind() method. The connection is not yet established to the server socket. However, the [ [ ...]

Useful Methods of DatagramSocket Class

1. Constructors DatagramSocket() Creates a datagram socket and binds it to any available port on the local host machine. This socket is also bound to all IP addresses. This means that the socket may be referred to by any IP address of the computer. protected DatagramSocket(DatagramSocketImpl impl) Constructs a datagram socket with the specified DatagramSocketImpl [ [ ...]

Useful Methods of DatagramPacket Class

1. Constructors DatagramPacket(byte[] buffer, int bytesToRead) Creates a DatagramPacket to hold received data. The receive() method of DatagramSocket reads bytesToRead bytes of data and stores in buffer. The bytesToRead must not be greater than buffer.iength else an IiiegaiArgumentException is thrown. DatagramPacket(byte[] buffer,int bytesToSend,InetAddress address,int port) Creates a DatagramPacket to hold data to be sent to [ [ ...]

Remote Method Invocation in Java

1. INTRODUCTION The network programs that we have developed so far use the concept of sockets. Although, socket provides a simple way to write network programs, it is neither very convenient nor the most powerful. This is because everything must be transferred over the network as a stream of bytes. Though, Java provides a rich [ [ ...]

Remote Method Invocation in Java: An Application

In this section, we shall develop a simple but elegant distributed application using Java RMI technology. In this application [Figure 14.4:], the server program creates and exports a simple remote object (we call it calculator) which provides one method. The method takes two integers as arguments and returns their sum. A client program gets a [ [ ...]

Compiling and Running the Program in JAVA

1. COMPILING THE PROGRAM Suppose the server application is developed in the directory E:\Net\rmi\caicuiator\server of a computer having IP address 172.16.5.81. Hereafter, we shall refer to this directory as server_home. Now, put server-side files in server_home as shown in Figure 14.7: (i) Assume that the client application is developed in the directory E:\Net\rmi\caicuiator\ciient of another [ [ ...]

Remote Method Invocation in Java: Callback

1. CALLBACK In a typical RMI application, clients invoke methods on remote objects created by the server. Callback mechanism (as the name suggests) allows server to call methods back on remote objects created and passed by the clients. This service is necessary in many cases. Consider the following situations: When a client invokes a method [ [ ...]

Dynamic Object Activation & Dynamic Class Downloading

1. DYNAMIC OBJECT ACTIVATION In our previous examples, remote objects run all the time even if no method on them is invoked. Java 2 and later releases allow us to register information about remote object implementations whose instance should be created and executed on demand, instead of running all the time. In fact, the RMI [ [ ...]

Remote Method Invocation in Java: An Example

In this section, we shall develop another powerful distributed application using RMI technology that makes use of the power of dynamic class downloading. In this application [Figure 14.17:], the server creates a remote object called scheduler, which accepts jobs from the clients, executes these jobs locally, calculates the execution time, and finally returns the output [ [ ...]

Java Mail API

1. E-MAIL An electronic mail (or simply email or e-mail), as its name suggests, is a digital version of a message (or letter). This concept was introduced much earlier than evolution of the Internet. Needless to say that the email system was very simple at that time. It was as simple as leaving a message [ [ ...]