283 lines
9.2 KiB
Markdown
283 lines
9.2 KiB
Markdown
# Tubelib Programmers Interface
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Tubelib supports:
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- StackItem exchange via tubes and
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- wireless data communication between nodes.
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## 1. StackItem Exchange
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Tubes represent connections between two nodes, so that it is irrelevant
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if the receiving node is nearby, or far away connected via tubes.
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The length of the tube is limited to 100 nodes.
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For StackItem exchange we have to distinguish the following roles:
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- client: An active node calling push/pull functions
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- server: A passive node typically with inventory, which will be called
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Client and server API use the following special parameters:
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- `side` the contact side where the items shall be pulled out or pushed in.
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This is one of B(ack), R(ight), F(ront), L(eft), D(own), U(p) according to the
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following diagram (view onto the placed node). It can be used to separate
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incoming items for different inventories.
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```
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Up Back
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| /
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+--|-----+
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/ o /|
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+--------+ |
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Left ----| |o---- Right
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| o | |
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| / | +
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| / |/
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+-/------+
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/ |
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Front |
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Down
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```
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- `player_name`: Normally the name of the player, who placed the pushing node.
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But this could also be used to identify the player interacting with the
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pushing node.
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The use of both parameters on server side is not required. See chap. 4 for an example
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of an inventory node.
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## 2. Data communication
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For the data communication an addressing method based on node numbers is used.
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Each registered node gets a unique node number with 4 figures (or more if needed).
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The numbers are stored in a storage list. That means, a new node, placed on
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the same position gets the same node number as the previously placed node on that
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position.
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The communication supports two services:
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- `send_message`: Send a message to one or more nodes without response
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- `send_request`: Send a messages to exactly one node and return the response
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It is up to the programmer, which messages shall be supported.
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But if a node can be switched on/off or started/stopped, use "on" and "off" as commands
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for both cases.
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## 3. API Functions
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### Register, Add, Remove Nodes
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Before a node can take part on the item exchange via tubes or data communication,
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it has to be registered once.
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```LUA
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tubelib.register_node(name, add_names, node_definition)
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```
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Call this function only at load time!
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Parameters:
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- name: The node name like "tubelib:pusher"
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- add_names: A table with additional node names if needed, e.g.: "tubelib:pusher_active"
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- node_definition: A table with the server callback functions according to:
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```LUA
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{
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on_pull_item = func(pos, side, player_name),
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-- Pull an item from the node inventory.
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-- The function shall return an item stack with one element
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-- like ItemStack("default:cobble") or nil.
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-- Param side: The node contact side, where the item shall be pulled out.
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-- Param player_name: Can be used to check access rights.
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on_push_item = func(pos, side, item, player_name),
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-- Push the given item into the node inventory.
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-- Param side: The node contact side, where the item shall be pushed in.
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-- Param player_name: Can be used to check access rights.
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-- The function shall return true if successful, or false if not.
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on_unpull_item = func(pos, side, item, player_name),
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-- Undo the previous pull and place the given item back into the inventory.
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-- Param side: The node contact side, where the item shall be unpulled.
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-- Param player_name: Can be used to check access rights.
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-- The function shall return true if successful, or false if not.
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on_recv_message = func(pos, topic, payload),
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-- Execute the requested message
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-- Param topic: A topic string like "on"
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-- Param payload: Additional data for more come complex commands,
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-- payload can be a number, string, or table.
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-- The function shall return true/false for commands like on/off
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-- or return the requested data for commands like a "state" request.
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}
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```
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**Each node has to call:**
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```LUA
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tubelib.add_node(pos, name)
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```
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`add_node` shall be called when the node is placed.
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The function is used to register the nodes position for the communication node
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number and to update the tube surrounding.
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`pos` the node position, `name` is the node name.
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```LUA
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tubelib.remove_node(pos)
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```
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'remove_node' shall be called then the node is dig.
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The function is used to remove the node number from the internal list.
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### Item Exchange via Tubes
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For item exchange as a pushing/pulling node the following functions exist:
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```LUA
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tubelib.pull_items(pos, side, player_name)
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```
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Pull one item from the given position specified by `pos` and `side`.
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Parameters:
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- `pos` is the own node position
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- `side` is the contact side, where the item shall be pulled in
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- `player_name` can be used to check access rights.
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- The function returns an item stack with one element like ItemStack("default:cobble") or nil.
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```LUA
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tubelib.push_items(pos, side, items, player_name)
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```
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Push one item to the given position specified by `pos` and `side`.
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Parameters:
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- `pos` is the own node position
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- `side` is the contact side, where the item shall be pushed out
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- `item` is an item stack with one element like ItemStack("default:cobble")
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- `player_name` can be used to check access rights.
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The function returns true if successful, or false if not.
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```LUA
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tubelib.unpull_items(pos, side, items, player_name)`
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```
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Undo the previous pull and place the item back into the inventory.
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Parameters:
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- `pos` is the own node position
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- `side` id the node contact side, where the item shall be unpulled
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- `player_name` can be used to check access rights.
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The function returns true if successful, or false if not.
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### Wireless Data Communication
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For data communication the following functions exist:
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```LUA
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tubelib.send_message(numbers, placer_name, clicker_name, topic, payload)
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```
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Send a message to all nodes referenced by `numbers`, a string with
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one or more destination node numbers separated by blanks.
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The message is based on a topic string (e.g. "start") and
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a topic related payload.
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The placer and clicker names are needed to check the protection rights.
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`placer_name` is the name of the player, who places the node.
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`clicker_name` is the name of the player, who uses the node.
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`placer_name` of sending and receiving nodes have to be the same.
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If every player should be able to send a message, use nil for `clicker_name`.
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Because several nodes could be addressed, the function don't return any response.
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```LUA
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tubelib.send_request(number, topic, payload)
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```
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In contrast to `send_message` this functions send a message to exactly one node
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referenced by `number` and returns the node response.
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The message is based on the topic string (e.g. "state") and
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topic related payload.
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## 4. Code Snippets
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### Register Node (from 'legacy_nodes.lua')
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```LUA
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tubelib.register_node("default:chest", {"default:chest_open"}, {
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on_pull_item = function(pos, side, player_name)
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local meta = minetest.get_meta(pos)
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return tubelib.get_item(meta, "main")
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end,
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on_push_item = function(pos, side, item, player_name)
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local meta = minetest.get_meta(pos)
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return tubelib.put_item(meta, "main", item)
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end,
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on_unpull_item = function(pos, side, item, player_name)
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local meta = minetest.get_meta(pos)
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return tubelib.put_item(meta, "main", item)
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end,
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})
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```
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### Add/remove node (from 'lamp.lua')
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```LUA
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after_place_node = function(pos, placer)
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local number = tubelib.add_node(pos, "tubelib:lamp")
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...
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end,
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after_dig_node = function(pos)
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tubelib.remove_node(pos)
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end,
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```
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### Item exchange via tubes (from 'pusher.lua')
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```LUA
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local items = tubelib.pull_items(pos, "L", player_name)
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if items ~= nil then
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if tubelib.push_items(pos, "R", items, player_name) == false then
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tubelib.unpull_items(pos, "L", items, player_name)
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end
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end
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```
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### Message communication (from 'button.lua')
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```LUA
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local number = meta:get_string("number")
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local placer_name = meta:get_string("placer_name")
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tubelib.send_message(number, placer_name, nil, "stop", nil)
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```
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### 5. Example Code
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Tubelib includes the following example nodes which can be used for study
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and as templates for own projects:
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- pusher.lua: a simple client pushing/pulling items
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- blackhole.lua: a simple server client, makes all items disappear
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- button.lua: a simple communication node, only sending messages
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- lamp.lua: a simple communication node, only receiving messages
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## 6. Further information
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The complete functionality is implemented in the file
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This file has further helper functions and is recommended for deeper study.
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## 7. History
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2017-10-02 First draft
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2017-10-29 Commands start/stop replaced by on/off
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2018-03-31 Corrections for 'send_request' and 'add_node'
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