Everything You Need to Know About Java Networking

What Is Java Networking?

Java networking is the concept of connecting two or more computing devices to share resources. The application layer of a Java program communicates with the network. The java.net package contains all of the Java networking classes and interfaces.

Common Network Protocols

The java.net package supports 2 protocols. These are their names:

1. The Transmission Control Protocol (TCP):

TCP enables secure communication between two applications. It is commonly applied together with the Internet Protocol, which is referred to as TCP/IP.

2. User Datagram Protocol (UDP):

UDP is a connectionless protocol allowing data packets to be sent between applications.

Advantages of Java Networking

Java has been used in a wide range of applications over the years due to the following benefits:

1. Ease

Java is a simple programming language that is simple to learn and understand. Its syntax is based on C++ and uses automatic garbage collection. It has also removed features such as explicit pointers, operator overloading, and so on, making it easier to read and write.

2. Object-Orientation

Java employs an object-oriented paradigm. As a result, everything in Java is an object handling both data and behavior, making it more practical.

3. Secure

Because it doesn't use explicit pointers, Java is a secure programming language. Java programs are also executed within the virtual machine sandbox. JRE also distinguishes between class packages from the local file system and those imported from the network.

4. Platform Independent

Java code can run directly on multiple platforms, eliminating the need to compile it each time.

5. Multi-Threaded

Java employs a multi-threaded environment in which a larger task can be divided into multiple threads and run independently. The main benefit of multi-threading is that we don't have to allocate memory to each running thread.

Java Networking Terminology

The following are the most commonly used Java networking terminologies:

• Internet Protocol Address

The IP address is a unique number assigned to a network node, such as 192.168.0.1. It is made up of octets of numbers ranging from 0 to 255.

• Protocol

A protocol is a set of communication rules:

• TCP
• FTP
• Telnet
• SMTP
• POP
• and so on.

• Port Number 

Each application is uniquely identified by its port number. It serves as a point of contact between applications. The port number is used in conjunction with an IP address to communicate between two applications.

• MAC Address

A MAC address is essentially a hardware identification number that uniquely identifies each network device. 

• Connection-Oriented and Connectionless Protocol

The receiver sends acknowledgment in the connection-oriented protocol. As a result, it is dependable but slow. TCP is an example of a connection-oriented protocol.

The receiver does not send acknowledgement in the connectionless protocol. As a result, it is unreliable but fast. UDP is an example of a connectionless protocol.

• Socket

In Java, a socket is one end of a two-way communication link between two programs running on a network. A socket is always associated with a port number to allow the TCP layer to identify the application to which data is being sent.

Java Networking Classes

The Java programming language's java.net package contains a number of classes that make it simple to access network resources. The following classes are included in the java.net package:

• CacheRequest

The CacheRequest class is applicable in Java whenever resources need to be stored in the ResponseCache. This class's objects serve as an edge for the OutputStream object to store resource data in the cache.

• CookieHandler

CookieHandler is a Java class that implements a callback mechanism for securing an HTTP state management policy implementation within the HTTP protocol handler. The HTTP state management mechanism defines how HTTP requests and responses are made.

• CookieManager

The CookieManager class is used to give a precise CookieHandler implementation. This class distinguishes cookie storage from cookie acceptance and rejection policy; a CookieManager comprises two parts: a CookieStore and a CookiePolicy.

• DatagramPacket

The DatagramPacket class provides a method for connectionless message transfer from one system to another. In addition, this class contains tools for creating datagram packets for connectionless transmission via the datagram socket class.

• InetAddress

The InetAddress class provides methods for obtaining the IP address of any hostname. An unsigned 32-bit or 128-bit number represents an IP address. InetAddress is capable of handling both IPv4 and IPv6 addresses.

• Server Socket

The ServerSocket class is used to implement the server-side of a client/server Socket Connection in a system-independent manner. If the ServerSocket class's function Object() { [native code] } cannot listen on the specified port, an exception is thrown. For example, if the port is already in use, it will throw an exception.

• Socket

The Socket class is used to create socket objects that aid users in performing all basic socket operations. Users can perform various networking tasks such as sending data, reading data, and closing connections.

• DatagramSocket

A network socket that provides a connectionless point for sending and receiving packets is the DatagramSocket class. Every packet sent from a datagram socket is routed and delivered individually. It can also be used to transmit and receive broadcast information.

• Proxy

A proxy is an unchanged object and a kind of tool, method, program, or system that serves to protect the data of its users and computers. It acts as a barrier between computers and internet users.

• URL

The URL class in Java is the gateway to any available internet sources. A Class URL is a Uniform Resource Locator (URL) that points to a "resource" on the World Wide Web.

• URLConnection

The URLConnection class in Java is an abstract class that describes a resource connection defined by a similar URL. The URLConnection class is used to help with two distinct but related tasks.

Java Networking Interfaces

Within the Java programming language, the Java.net package includes several interfaces that make it simple to access network resources. The following interfaces are included in the java.net package:

• CookiePolicy

The java.net package's CookiePolicy interface provides classes for implementing various networking applications. It determines which cookies are accepted and which are rejected. There are 3 pre-defined policy implementations in CookiePolicy:

• ACCEPT_ALL
• ACCEPT_NONE
• ACCEPT_ORIGINAL_SERVER.

• CookieStore

A CookieStore is an interface that describes a cookie storage space. CookieManager adds cookies to the CookieStore with each HTTP response and retrieves cookies from the CookieStore with each HTTP request.

• FileNameMap

The FileNameMap interface is a simple interface that implements a tool for highlighting a file name and a MIME type string. FileNameMap reads a data file and charges a filename map (also known as a mimetable).

• SocketOption

The SocketOption interface allows users to control how sockets behave. It is frequently necessary to develop necessary features in Sockets. SocketOption lets the user configure a variety of standard options.

• SocketImplFactory

The SocketImplFactory interface defines a SocketImpl instance factory. The socket class uses it to create socket implementations that implement several policies.

• ProtocolFamily

This interface illustrates a communication protocol family. The ProtocolFamily interface includes a name() method that returns the protocol family's name.

Socket Programming

Socket programming is a method of communicating between two nodes on a network. One socket (node) listens on a specific port at an IP address, while the other socket reaches out to form a connection. While the client attempts to contact the server, the server creates the listener socket.

The steps involved in establishing a TCP connection between two computers using socket programming are as follows:

• Step 1 - The server creates a ServerSocket object and specifies which port number communication will take place.
• Step 2 - After the ServerSocket object is instantiated, the server invokes the ServerSocket class's accept() method. This program waits for a client to connect to the server on the specified port.
• Step 3 - While the server is idle, a client creates an object of the Socket class and specifies the server name and port number to connect to.
• Step 4 - Following the preceding step, the function Object() { [native code] } of the Socket class attempts to connect the client to the specified server and port number. If communication is authenticated, the client receives a Socket object capable of interacting with the server.
• Step 5 - The accept() method on the server returns a reference to a new socket on the server that is connected to the client's socket.

After the connections have been stabilized, communication can take place via I/O streams. A socket class object has an OutputStream as well as an InputStream. The OutputStream of the client is connected to the server's InputStream, which is then combined with the server's OutputStream. TCP or Transmission Control Protocol is a two-way communication protocol. As a result, information can be transmitted over both streams simultaneously.

Socket Class

The domain java.net. The Socket class allows us to create socket objects that aid in implementing all basic socket operations. Users can perform various networking tasks such as sending data, reading data, and closing connections. Java.net was used to create each Socket object. One remote host has been specifically associated with the socket class. If a user wishes to connect to another host, he must first create a new socket object.

ServerSocket Class Methods

• public void connect ()

This method connects a specific host to the socket. This method is only required when the user uses the no-argument function to create the socket.

• public int getPort ()

This method returns the port on the remote machine to which the socket is pinned.

• public InetAddress getInetAddress ()

This method returns the other computer's address to which the socket is connected.

• public int getLocalPort ()

This method is used to return the port to the local machine to which the socket is connected.

• public SocketAddress getRemoteSocketAddress ()

This method returns the remote socket's location.

• public InputStream getInputStream () 

This method is used to return the socket's input stream. This input stream is combined with the remote socket's output stream.

• public OutputStream getOutputStream ()

This method is used to return the socket's output stream. The output stream is combined with the remote socket's input stream.

• public void close () 

This method closes the socket, preventing the Socket class object from connecting to any server again.

Java.net Package

Java programs are designed to run over a network. This package includes a set of classes for practicing these network applications. These classes are as follows:

1. Authenticator
2. CacheRequest
3. CacheResponse
4. ContentHandler
5. CookieHandler
6. CookieManager
7. DatagramPacket
8. DatagramSocket
9. DatagramSocketImpl
10. InterfaceAddress
11. JarURLConnection
12. MulticastSocket
13. InetSocketAddress
14. InetAddress
15. Inet4Address
16. Inet6Address
17. IDN
18. HttpURLConnection
19. HttpCookie
20. NetPermission
21. NetworkInterface
22. PasswordAuthentication
23. Proxy
24. ProxySelector
25. ResponseCache
26. SecureCacheResponse
27. ServerSocket
28. Socket
29. SocketAddress
30. SocketImpl
31. SocketPermission
32. StandardSocketOptions
33. URI
34. URL
35. URLClassLoader
36. URLConnection
37. URLDecoder
38. URLEncoder
39. URLStreamHandler

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