turtle.lua

local modem = peripheral.find("modem")

rednet.open("left")

io.write("Input HUB ID: ")

local hubID = tonumber(read())

rednet.send(hubID, "connectMsg")

local id, message = rednet.receive()
if message == "connectSuccess"  then
    print("Connected to HUB." )
    else
    print("ERROR: Check HUB ID is correct.")
end