Template

;; create a breed of turtles that the students control through the clients
;; there will be one student turtle for each client.
breed [ students student ]

students-own
[
  user-id   ;; students choose a user name when they log in whenever you receive a
            ;; message from the student associated with this turtle hubnet-message-source
            ;; will contain the user-id
  step-size ;; you should have a turtle variable for every widget in the client interface that
            ;; stores a value (sliders, choosers, and switches). You will receive a message
            ;; from the client whenever the value changes. However, you will not be able to
            ;; retrieve the value at will unless you store it in a variable on the server.
]

;; the STARTUP procedure runs only once at the beginning of the model
;; at this point you must initialize the system.

to startup
  hubnet-reset
end 

to setup
  clear-patches
  clear-drawing
  clear-output
  ;; during setup you do not want to kill all the turtles
  ;; (if you do you'll lose any information you have about the clients)
  ;; so reset any variables you want to default values, and let the clients
  ;; know about the change if the value appears anywhere in their interface.
  ask turtles
  [
    set step-size 1
    hubnet-send user-id "step-size" step-size
  ]
  ;; calling reset-ticks enables the 'go' button
  reset-ticks
end 

to go
  ;; process incoming messages and respond to them (if needed)
  ;; listening for messages outside of the every block means that messages
  ;; get processed and responded to as fast as possible
  listen-clients
  every 0.1
  [
    ;; tick (and display) causes world updates messages to be sent to clients
    ;; these types of messages should only be sent inside an every block.
    ;; otherwise, the messages will be created as fast as possible
    ;; and consume your bandwidth.
    tick
  ]
end 

;;
;; HubNet Procedures
;;

to listen-clients
  ;; as long as there are more messages from the clients
  ;; keep processing them.
  while [ hubnet-message-waiting? ]
  [
    ;; get the first message in the queue
    hubnet-fetch-message
    ifelse hubnet-enter-message? ;; when clients enter we get a special message
    [ create-new-student ]
    [
      ifelse hubnet-exit-message? ;; when clients exit we get a special message
      [ remove-student ]
      [ ask students with [user-id = hubnet-message-source]
        [ execute-command hubnet-message-tag ] ;; otherwise the message means that the user has
      ]                                        ;; done something in the interface hubnet-message-tag
                                               ;; is the name of the widget that was changed
    ]
  ]
end 

;; when a new user logs in create a student turtle
;; this turtle will store any state on the client
;; values of sliders, etc.

to create-new-student
  create-students 1
  [
    ;; store the message-source in user-id now
    ;; so when you get messages from this client
    ;; later you will know which turtle it affects
    set user-id hubnet-message-source
    set label user-id
    ;; initialize turtle variables to the default
    ;; value of the corresponding widget in the client interface
    set step-size 1
    ;; update the clients with any information you have set
    send-info-to-clients
  ]
end 

;; when a user logs out make sure to clean up the turtle
;; that was associated with that user (so you don't try to
;; send messages to it after it is gone) also if any other
;; turtles of variables reference this turtle make sure to clean
;; up those references too.

to remove-student
  ask students with [user-id = hubnet-message-source]
  [ die ]
end 

;; Other messages correspond to users manipulating the
;; client interface, handle these individually.

to execute-command [command]
  ;; you should have one if statement for each widget that
  ;; can affect the outcome of the model, buttons, sliders, switches
  ;; choosers and the view, if the user clicks on the view you will receive
  ;; a message with the tag "View" and the hubnet-message will be a
  ;; two item list of the coordinates
  if command = "step-size"
  [
    ;; note that the hubnet-message will vary depending on
    ;; the type of widget that corresponds to the tag
    ;; for example if the widget is a slider the message
    ;; will be a number, of the widget is switch the message
    ;; will be a boolean value
    set step-size hubnet-message
    stop
  ]
  if command = "up"
  [ execute-move 0 stop ]
  if command = "down"
  [ execute-move 180 stop ]
  if command = "right"
  [ execute-move 90 stop ]
  if command = "left"
  [ execute-move 270 stop ]
end 

;; whenever something in world changes that should be displayed in
;; a monitor on the client send the information back to the client

to send-info-to-clients ;; turtle procedure
  hubnet-send user-id "location" (word "(" pxcor "," pycor ")")
end 

to execute-move [new-heading]
  set heading new-heading
  fd step-size
  send-info-to-clients
end 


; Public Domain:
; To the extent possible under law, Uri Wilensky has waived all
; copyright and related or neighboring rights to this model.