lock server

local client = changeme
local usr = "changeme"
local pass = "changeme"
rednet.open("back")

-- Helper function to split strings at the first line-break ("n").
-- Returns: Two strings representing the first and second half of the given string.
local function splitAtLineBreak( toSplit )
  for i = 1, #toSplit do
  local currChar = string.sub( toSplit, i, i )
  if currChar == "n" then
    firstHalf = string.sub( toSplit, 1, i - 1 )
    secondHalf = string.sub( toSplit, i + 1 )

    return firstHalf, secondHalf
  end  -- of IF
  end  -- of FOR
end

while true do
  local id, loginDetails
  repeat
    id, loginDetails = rednet.receive()
  until id == client

  local receivedUser, receivedPass = splitAtLineBreak( loginDetails )
  if receivedUser == usr and receivedPass == pass then
    sleep(5)
    rednet.send(client, "granted")
  else
    sleep(5)
    rednet.send(client, "denied")
  end
end