Client

-- client
local modemSide = "right"
local serverId = 6
rednet.open(modemSide)

local function updateFile(name)
  print('sending file request for: '..name)
  rednet.send(serverId, name)
  while true do
    print('waiting for response')
    local event, id, msg, dist = os.pullEvent("rednet_message")
    if id == serverId then
      msg = textutils.unserialize(msg)
      if not msg.success then
        printError(msg.message)
      else
        local handle = fs.open(msg.path, "w")
        if not handle then
          printError("Failed to open file to update")
        elseif not msg.message then
          printError("No contents received")
        else
          handle.write(msg.message)
          handle.close()
        end
      end
      return -- exit out of the function, we are done here
    else
      printError('response from unknown client')
    end
  end
end

updateFile("cake")
updateFile("can")
updateFile("someFile")

rednet.close(modemSide)