| Please Note|
Rednet no longer supports transmitting data through Bundled Cables. However, interacting with Bundled Cables is still available via the Redstone API.
The Rednet API allows computers to communicate between themselves without using redstone wires. In order to send and receive data, a modem is required. The data is received immediately after sending it, but only by computers within a certain range. That range depends on the altitude of the sending computer increasing with higher altitudes to a max of 384. NOTE: The distance variable that is sent/received through the Rednet API is based off of the computer location, not the modem location.
|rednet.open(string side)||Tells the computer that the side can be used for networking.|
|rednet.close(string side)||Tells the computer that the side can no longer be used for networking.|
|rednet.announce()||Broadcasts an empty rednet message.|
|rednet.send(number receiverID, string message)||Sends a message intended for another system with a specific ID using the currently opened sides. The receiver ID is the ID number (note - not a string) of the computer you're sending the message to. Later versions or ComputerCraft allow some other data types as the message.|
|rednet.broadcast(string message)||Sends the message to ALL connected and open computers.|
|rednet.receive([ number timeout ])||Waits until it received a rednet message or until timeout seconds have passed. Leave args empty to wait for a message indefinitely.|
|rednet.isOpen(string side)||Returns true if the wireless modem is open.|
|rednet.run()||Internal use function - need not be called directly. Waits for modem_message events to appear within the event queue and generates corresponding rednet_message events for use with this API.|
|rednet_message||Fired when a rednet message is received (can be used as alternative for rednet.receive())||number senderId, string message, number distance|
Before the creation of the in-game wireless networking API, the term "Rednet" referred to a system created by one of the ComputerCraft users based on bundled cables from a popular Minecraft mod - RedPower. It also allowed communication between computers, but the data was transferred slowly - every bit was converted to redstone signal, that lasted about 0,05 seconds. On the release of ComputerCraft 1.3, the system became useless, as the wireless networking was officially implemented to the mod.
ID Whitelists are useless, and messages sent by Rednet can be viewed by anyone, even if they are not the target computer.
Rednet alone is completely insecure. Any messages sent via rednet can actually be sniffed, contrary to popular belief, and people can pretend to be a certain computer and fool rednet easily.
Rednet simply utilizes the Modem API. A user can easily sniff and find out what messages a computer is receiving if he knows its ID. All he has to do is use the Modem API to listen, where the channel to listen on is the target computer's ID. Additionally, a malicious user can 'pretend' to be a certain computer by using the Modem API to send a message to the target computer's ID with the message, but using the ID of the computer to pretend to be for the reply channel parameter. If they do so, the computer receiving the message with rednet will be fooled into thinking it came from a different computer.
When using rednet for anything with security critical, be sure to implement your own security measures.
Overview: Rednet functions by having a modem listen on the channel of the computer's ID, and the rednet broadcast channel for messages. It uses the replyChannel parameter of the modem_message event as the sender computer's ID. It broadcasts by sending a simple modem message on the rednet broadcast channel, and receives by receiving a modem message on the broadcast channel or the channel of its computer's ID.
(local) tValidSides: Contains valid values of strings containing computer sides, used by open and close
rednet.open(sSide): Checks if sSide is a string, a valid side, and a side with a modem on it. Then it opens the modem on CHANNEL_BROADCAST and os.getComputerID()
rednet.close(sSide): Checks if sSide is a string, a valid side, and a side with a modem on it. Then it closes the modem on CHANNEL_BROADCAST and os.getComputerID()
rednet.isOpen(sSide): Checks if sSide is a string, a valid side, and a side with a modem on it. Then it returns true if the modem on sSide is open on both CHANNEL_BROADCAST and os.getComputerID()
rednet.send(nRecipient, sMessage): For each side sSide in rs.getSides(), it calls isOpen(sSide). If the result is true, it executes
peripheral.call( sSide, "transmit", nRecipient, os.getComputerID(), sMessage )
rednet.broadcast(sMessage): Calls send(CHANNEL_BROADCAST, sMessage)
rednet.receive(nTimeout): If nTimeout is there, it starts a timer for nTimeout seconds-stored in timer, and sets sFilter to nil. Otherwise, sFilter is set to "rednet_message". In a loop,
local e, p1, p2, p3, p4, p5 = os.pullEvent( sFilter )
is called. If e is "rednet_message" then it returns p1, p2, and p3, but if e is "timer", and p1 is timer then it returns nil.
(local) bRunning: false
rednet.run(): If bRunning is true, then it errors "rednet is already running". It then sets bRunning to true to indicate that it is running. Looping while bRunning, it pulls
local sEvent, sSide, sChannel, sReplyChannel, sMessage, nDistance = os.pullEventRaw( "modem_message" )
Then if sEvent is "modem_message", isOpen(sSide) is true, and sChannel is os.getComputerID() or it is CHANNEL_BROADCAST, then it queues
os.queueEvent( "rednet_message", sReplyChannel, sMessage, nDistance )