JINI Spontaneous Networking in Java

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Java User Group Torino
JINISpontaneous Networking in Java
Third Part Discovery and Join in-depth.
JUG_at_Webbit, Padova 9-10-11 Maggio 2003
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Topics

• In-depth view of Discovery
• In-depth view of Join
• The DEMO

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About the JUG

• The JUG was born in February 2002 by the idea of
  some Java fans in the Torino area
• The aim of the group is to promote the knowledge
  exchange between members and to create an
  important community in the landscape of Italian
  Java programmers
• Participating is free and voluntary
• You can participate at the meeting, write
  articles, expose your doubts, ask for support etc
  etc .... .... ....

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Who am I?

• Renzo Borgatti is a Java developer since 2000
• I was involved in several projects during my
  activity mainly focused on server side Java and
  J2EE
• I spend the rest of my time (too short!) playing
  piano, running and, of course, partecipating at
  the JUG activities!
• Feel free to contact me at renzo.borgatti_at_jugtorin
  o.it

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The discovery phase
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Network concepts
DISCOVERY

• Multicast special addresses of the IP range from
  224.0.0.0 to 239.255.255.255
• Unicast the classic communication model where
• UDPUser Datagram Protocol runs on the top of the
  IP. A connectionless, unreliable, datagram packet
  service
• TCP a reliable, stream oriented full duplex
  connection

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Kind of discovery
DISCOVERY

• Multicast Discovery Request
• Multicast reqUDP from the e. to the l.s.
• Unicast resTCP from the l.s. to the e.
• Multicast Discovery Announcement
• Multicast reqUDP from the l.s. to the e.
• Unicast reqTCP from the e. to the l.s.
• Unicast resTCP from the l.s. to the e.
• Unicast Discovery Request
• Unicast reqTCP from the e. to the l.s.
• Unicast resTCP from the l.s. to the e.
• Unicast Discovery Announcement
• Unicast reqTCP from the l.s. to the e.
• Unicast reqTCP from the e. to the l.s.
• Unicast resTCP from the l.s. to the e.

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Discovery overview
DISCOVERY
JVM
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Multicast request
DISCOVERY
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Unicast response
DISCOVERY
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Request datagram format
DISCOVERY
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The Join phase
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Overview
JOIN

• JINI entities have already found the lookup
  service
• In the Join phase, JINI entities start using the
  lookup service functionality
• Services register themselves
• Clients lookup services by interface

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The ServiceRegistrar interface
JOIN

• The method register() can be used by services to
  join or re-join the federation
• The service passes as a parameter a
  net.jini.core.lookup.ServiceItem object group
• Service object (the interface of the service
  exposed to the clients of the service)
• Attributes (any other objects needed to interact
  with the service such as icons, GUI elements and
  so forth)
• Returns a net.jini.core.lookup.ServiceRegistration
  which is a container for registration
  information (such as ServiceID)

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Registring services
JOIN
At the end ...
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Lookup
JOIN
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End of the Lookup
JOIN
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JINI Packages

• net.jini.core. --gt The core Jini classes
• net.jini. --gt contains libraries built using
  core packages
• com.sun.jini. --gt a set of helper classes
  considered non-standard and subject to change

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Demo...
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Some considerations

• When a client asks for a service in JINI
  federation has to assume that the services it
  wants have a common and well known interface
• This is because a client lookups a service by the
  mean of Java types (interfaces)
• How can I make such an assumption?
• For example how my client could find a printer
  service if it doesn't know nothing about that
  printer interface? Printer service can be
  different from federation to federation

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What a JINI client has to worry about?

• A client doesnt need to know
• how the service is implemented (the class
  implementation will be loaded at runtime)
• if the service is remote and how the service
  communicates with the remote skeleton (it depends
  on the implementation)
• how dependent classes (classes the client needs
  to run the service) appear into the classpath
• Otherwise a client needs to
• have services interfaces in the classpath
• Know how service behaves
• Have jini-core.jar library in the classpath

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Resources