Networking In Java
Networking supplements a lot of power to simple programs. With networks, a single program can regain information stored in millions of computers positioned anywhere in the world. Java is the leading programming language composed from scratch with networking in mind. Java Networking is a notion of combining two or more computing devices together to share resources.
Common Network Protocols
As stated earlier, the java.net package of the Java programming language includes various classes and interfaces that provide an easy-to-use means to access network resources.
Other than classes and interfaces, the java.net package also provides support for the two well-known network protocols. These are:
Transmission Control Protocol (TCP)
TCP or Transmission Control Protocol allows secure communication between different applications.
TCP is a connection-oriented protocol which means that once a connection is established, data can be transmitted in two directions.
This protocol is typically used over the Internet Protocol.
Therefore, TCP is also referred to as TCP/IP. TCP has built-in methods to examine for errors and ensure the delivery of data in the order it was sent, making it a complete protocol for transporting information like still images, data files, and web pages.
User Datagram Protocol (UDP)
UDP or User Datagram Protocol is a connection-less protocol that allows data packets to be transmitted between different applications.
UDP is a simpler Internet protocol in which error-checking and recovery services are not required.
In UDP, there is no overhead for opening a connection, maintaining a connection, or terminating a connection.
In UDP, the data is continuously sent to the recipient, whether they receive it or not.
Java Networking Terminology
In Java Networking, many terminologies are used frequently. These widely used Java Networking Terminologies are given as follows:
An IP address is a unique address that distinguishes a device on the internet or a local network. IP stands for “Internet Protocol.” It comprises a set of rules governing the format of data sent via the internet or local network. IP Address is referred to as a logical address that can be modified. It is composed of octets. The range of each octet varies from 0 to 255.
Range of the IP Address – 0.0.0.0 to 255.255.255.255
For Example – 192.168.0.1
A port number is a method to recognize a particular process connecting internet or other network information when it reaches a server. The port number is used to identify different applications uniquely. The port number behaves as a communication endpoint among applications. The port number is correlated with the IP address for transmission and communication among two applications. There are 65,535 port numbers, but not all are used every day.
A network protocol is an organized set of commands that define how data is transmitted between different devices in the same network. Network protocols are the reason through which a user can easily communicate with people all over the world and thus play a critical role in modern digital communications. For Example – TCP, FTP, POP, etc.
MAC address stands for Media Access Control address. It is a bizarre identifier that is allocated to a NIC (Network Interface Controller/ Card). It contains a 48 bit or 64-bit address, which is combined with the network adapter. MAC address can be in hexadecimal composition. In simple words, a MAC address is a unique number that is used to track a device in a network.
A socket is one endpoint of a two-way communication connection between the two applications running on the network. The socket mechanism presents a method of inter-process communication (IPC) by setting named contact points between which the communication occurs. A socket is tied to a port number so that the TCP layer can recognize the application to which the data is intended to be sent.
Connection-oriented and connection-less protocol
In a connection-oriented service, the user must establish a connection before starting the communication. When the connection is established, the user can send the message or the information, and after this, they can release the connection. However, In connectionless protocol, the data is transported in one route from source to destination without verifying that the destination is still there or not or if it is ready to receive the message. Authentication is not needed in the connectionless protocol.
Example of Connection-oriented Protocol – Transmission Control Protocol (TCP)
Example of Connectionless Protocol – User Datagram Protocol (UDP)
Java Networking classes
The java.net package of the Java programming language includes various classes that provide an easy-to-use means to access network resources. The classes covered in the java.net package are given as follows –
The CacheRequest class is used in java whenever there is a need to store resources in ResponseCache. The objects of this class provide an edge for the OutputStream object to store resource data into the cache.
The CookieHandler class is used in Java to implement a callback mechanism for securing up an HTTP state management policy implementation inside the HTTP protocol handler. The HTTP state management mechanism specifies the mechanism of how to make HTTP requests and responses.
The CookieManager class is used to provide a precise implementation of CookieHandler. This class separates the storage of cookies from the policy surrounding accepting and rejecting cookies. A CookieManager comprises a CookieStore and a CookiePolicy.
The DatagramPacket class is used to provide a facility for the connectionless transfer of messages from one system to another. This class provides tools for the production of datagram packets for connectionless transmission applying the datagram socket class.
The InetAddress class is used to provide methods to get the IP address of any hostname. An IP address is expressed by a 32-bit or 128-bit unsigned number. InetAddress can handle both IPv4 and IPv6 addresses.
The ServerSocket class is used for implementing system-independent implementation of the server-side of a client/server Socket Connection. The constructor for ServerSocket class throws an exception if it can’t listen on the specified port. For example – it will throw an exception if the port is already being used.
The Socket class is used to create socket objects that help the users in implementing all fundamental socket operations. The users can implement various networking actions such as sending, reading data, and closing connections. Each Socket object built using java.net.Socket class has been connected exactly with 1 remote host; for connecting to another host, a user must create a new socket object.
The DatagramSocket class is a network socket that provides a connection-less point for sending and receiving packets. Every packet sent from a datagram socket is individually routed and delivered. It can further be practiced for transmitting and accepting broadcast information. Datagram Sockets is Java’s mechanism for providing network communication via UDP instead of TCP.
A proxy is a changeless object and a kind of tool or method or program or system, which serves to preserve the data of its users and computers. It behaves like a wall between computers and internet users. A Proxy Object represents the Proxy settings to be applied with a connection.
The URL class in Java is the entry point to any available sources on the internet. A Class URL describes a Uniform Resource Locator, which is a signal to a “resource” on the World Wide Web. A source can denote a simple file or directory, or it can indicate a more difficult object, such as a query to a database or a search engine.
The URLConnection class in Java is an abstract class describing a connection of a resource as defined by a similar URL. The URLConnection class is used for assisting two distinct yet interrelated purposes. Firstly it provides control on interaction with a server(especially an HTTP server) than a URL class. Furthermore, with a URLConnection, a user can verify the header transferred by the server and can react consequently. A user can also configure header fields used in client requests using URLConnection.
Java Networking Interfaces
The java.net package of the Java programming language includes various interfaces also that provide an easy-to-use means to access network resources. The interfaces included in the java.net package are as follows:
The CookiePolicy interface in the java.net package provides the classes for implementing various networking applications. It decides which cookies should be accepted and which should be rejected. In CookiePolicy, there are three pre-defined policy implementations, namely ACCEPT_ALL, ACCEPT_NONE, and ACCEPT_ORIGINAL_SERVER.
A CookieStore is an interface that describes a storage space for cookies. CookieManager combines the cookies to the CookieStore for each HTTP response and recovers cookies from the CookieStore for each HTTP request.
The FileNameMap interface is an uncomplicated interface that implements a tool to outline a file name and a MIME type string. FileNameMap charges a filename map ( known as a mimetable) from a data file.
The SocketOption interface helps the users to control the behavior of sockets. Often, it is essential to develop necessary features in Sockets. SocketOptions allows the user to set various standard options.
The SocketImplFactory interface defines a factory for SocketImpl instances. It is used by the socket class to create socket implementations that implement various policies.
This interface represents a family of communication protocols. The ProtocolFamily interface contains a method known as name(), which returns the name of the protocol family.⌖ core java java-networking programming tcp udp