Java Network Programming Libraries and Functions

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Java Network Programming Libraries and Functions

• Paul Stockdale

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Javas Network Class Libraries

• The two main packages for dealing with network
  functions in Java are
• java.net
• java.rmi

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The java.net Package

• Two distinct categories of classes within
  java.net package
• The Sockets API
• Tools for working with URLs

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Sockets API

• Sockets are a low-level programming interface for
  networked communications, sending data streams
  between applications on the same or different
  hosts
• The java.net package makes socket programming
  relatively simple by providing a simplified,
  object oriented interface
• Network I/O uses Javas stream classes to read
  and write remotely, in the same way it would do
  locally

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Three Types of Socket Class

• java.net.Socket
• java.net.DatagramSocket
• java.net.MuliticastSockets

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Protocols

• Java only supports the Internet Protocol (IP)
• The Socket class uses TCP (connection-oriented)
• The DatagramSocket class uses UDP (connectionless)

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Socket Class

• Uses TCP, a connection-oriented protocol
• Connection stays open even if no data is being
  sent
• Data arrives in order it was sent
• Data delivery is guarenteed

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Clients and Servers

• The Socket class is used by both client and
  server ends of a connection
• Server also uses java.net.ServerSocket class to
  listen for new client connections
• Server can use multiple Socket objects to
  simultaneously connect to multiple clients

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DatagramSocket Class

• Uses UDP, a connectionless protocol
• End-to-end connections not set up in advance
• Data is not kept in any order
• No guarantee of data delivery

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MulticastSocket Class

• Variation of DatagramSocket Class
• Sends to multiple recipients simultaneously
• Not widely supported on the Internet

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The java.rmi Package

• Remote Method Invocation allows Java objects to
  communicate across a network
• Applications can work with objects on remote
  hosts as if they were local
• java.rmi provides a means for writing distributed
  applications using Java objects instead of data
  streams

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Remote Method Invocation

• Objects must be serialisable
• Objects are passed by reference
• Method invocations occur on the original object

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RMI registry

• Used to look up references to registered remote
  objects
• Requires the rmiregistry application to be
  running on the local host
• Unsophisticated and slow
• Intended only to bootstap RMI communications
• Other name services can be used

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References

• Niemeyer, P. and Knudsen, J. (June 2002) Learning
  Java 2nd Edition. Sebastopol, CA OReilly.