Rudimentary Client-Server Message Board Ricky Landry COP5611

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Rudimentary Client-ServerMessage Board Ricky
LandryCOP5611 Operating Systems Design
PrinciplesUniversity of Central FloridaApril
16, 2012
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Fundamental Requirements

• Ability to create topics
• Ability to create comments associated with a
  topic
• Ability to produce information on the author of a
  topic or comment
• Ability to produce the timestamp of creation and
  last modification time of a topic or a comment
• Ability to remove a topic or comment (only if
  requested by the author)

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Critical Design Decisions

• Client-Server Architecture
• Multi-threaded Server
• Stateless
• Messaging Protocol
• Java Swing Client Front-End (GUI)

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Message Board Database

• Server-side database was written specifically for
  the application to explore design challenges
• Multi-threaded server design required mutually
  exclusive access to the database to handle
  concurrency and atomicity concerns
• Accomplished through the use of object locks
  built into the Java language
• synchronized(this) wraps database access
  calls

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Server Database Design

• Singleton-patterned database consists of
• List of MbdbTopic objects, stored as a Hashtable
• List of MbdbComment objects, stored as a Hashtable

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Server Database Design

• MbdbTopic object consists of
• topic name
• author name
• creation time
• topic header
• deleted state
• list of the comment headers of child comments

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Server Database Design

• MbdbComment object consists of
• comment message
• author name
• creation time
• comment header
• deleted state
• unique identifier of its parent topic

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Server Database Design

• TopicHeader and CommentHeader Objects contain
• Topic/Comment unique identifier
• Topic/Comment last update time
• Definition of TopicHeaderList and
  CommentHeaderList containers, respectively

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Server Design

• Used the Java Serialization API for serialized
  object transfer between server and client.
• Listen socket is a Java ServerSocket object
• When a connection is made, the new socket
  connected to the client is handed off to a worker
  thread spawned specifically for the client

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Server Design
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Protocol Design

• Defines the following aspects of the
  client-server model
• Credentials
• Topic message data payloads
• Comment message data payloads
• Message structure
• Message types

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Protocol Design

• Client-to-Server Message Types
• CREATE_TOPIC
• CREATE_COMMENT
• REMOVE_TOPIC
• REMOVE_COMMENT
• GET_TOPIC_HEADERS
• GET_TOPIC_OBJECT
• GET_COMMENT_OBJECT
• CREDENTIALS
• CLOSING_CONNECTION

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Protocol Design

• Server-to-Client Message Types
• TOPIC_HEADERS_REPLY
• TOPIC_OBJECT_REPLY
• COMMENT_OBJECT_REPLY
• AUTHETICATION_SUCCESS
• AUTHETICATION_FAILURE
• INVALID_TOPIC_ID
• INVALID_COMMENT_ID
• INVALID_REPLY_RECEIVED

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Client Database Design

• The client has its own database that contains the
  client state
• Has four containers
• One containing MbdbTopic objects
• One containing MbdbComment objects
• One containing the read state for each topic
• One containing the read state for each comment
• Defines wrappers for Topic/Comment objects and
  their respective read state

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Client Database Design
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Client Controller Design

• Responsible for client database management and
  access
• Updates the client database with server data
• Provides current (undeleted) client data to the
  front-end
• Responsible for communication with the server
• Responsible for managing client credentials

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Client Front-End Design

• Built using the Java Swing API
• Provides basic interface to underlying function

Topic Window Mockup
Comment Window Mockup
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Client Front-End Design
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Client Front-End Design
Topic Window
Comment Window
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Questions

• ?