/** File is: HostServer.java 10-24-05  Version 1.0

Author Clark Elliott. Status: throw-away code to illustrate some points for class.

NOTE: This is NOT a suggested implementation for your agent platform,
but rather a running example of something that might serve some of
your needs, or provide a way to start thinking about what YOU would like to do.
You may freely use this code as long as you improve it and write your own comments.

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TO EXECUTE: 

1. Start the HostServer in some shell. >> java HostServer

1. start a web browser and point it to http://localhost:1565. Enter some text and press
the submit button to simulate playing the animal game.

2. start a second web browser, also pointed to http://localhost:1565 and do the same. Note
that the two agents do not interfere with one another.

3. To suggest to an agent that it migrate, enter the string "migrate"
in the text box and submit. The agent will migrate to a new port, but keep its old state.

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COMMENTS:

This is a simple framework for hosting agents that can migrate from
one server and port, to another server and port. For the example, the
server is always localhost, but the code would work the same on
different, and multiple, hosts.

State is implemented simply as an integer that is incremented. This represents the state
of the animal game for some agent.

The example uses a standard, default, HostListener port of 1565.

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DESIGN OVERVIEW

Here is the high-level design, more or less:

HOST SERVER
  Runs on some machine
  Port counter is just a global integer incrememented after each assignment
  Loop:
    Accept connection with a request for hosting
    Spawn an Agent Looper/Listener with the new, unique, port

AGENT LOOPER/LISTENER
  Make an initial state, or accept an existing state if this is a migration
  Get an available port from this host server
  Set the port number back to the client which now knows IP address and port of its
         new home.
  Loop:
    Accept connections from web client(s)
    Spawn an agent worker, and pass it the state and the parent socket blocked in this loop
  
AGENT WORKER
  If normal interaction, just update the state, and pretend to play the animal game
  (Migration should be decided autonomously by the agent, but we instigate it here with client)
  If Migration:
    Select a new host
    Send server a request for hosting, along with its state
    Get back a new port where it is now already living in its next incarnation
    Send HTML FORM to web client pointing to the new host/port.
    Wake up and kill the Parent AgentLooper/Listener by closing the socket
    Die

WEB CLIENT
  Just a standard web browser pointing to http://localhost:1565 to start.

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