I'm using ComputerCraft, a minecraft mod that adds computers, modems, and other peripherals. In this mod, you can write code using Lua

Question

This is my first time using Lua, and with following a tutorial, Im making a chat program, allowing two players to send and receive messages to each other. The receiving is called chatreceive.lua. The script is:

rednet.open("right")
sender, message = rednet.receive()
print("computer " .. sender .. " has sent :")
print(message)

I keep getting an error saying

chatreceive.lua:3: attempt to concatenate global 'sender' (a nil value)

Any solutions? Ive been trying for a while now

You should ensure `sender` is not nil, you can't concatenate a nil value. For instance `if (sender and message) then`. — csaar, Jul 16 '21 at 12:21

score 0 · Answer 1 · answered Mar 14 '22 at 06:14

That means that the variable 'sender' was nil. This probably means that there was some sort of error with rednet. You should add a lot of checks to make sure your programs don't fail in critical situations:

if sender==nil then
  print("SENDER IS NIL!!!")
end

Also, what version of CC are you using? You shoud be more specific, to get better answers...

I'm using ComputerCraft, a minecraft mod that adds computers, modems, and other peripherals. In this mod, you can write code using Lua

1 Answers1