TCP receive with DENON Amplifier

[Hadeel]

Hi!
I am trying to connect DENON Amplifier with TCP. 
While I can send message successfully to DENON, I cannot receive reply from it.
With my laptop I tried TCP with telnet and confirmed that DENON gives back response to my terminal.

Following is what I have tried with resident script (interval = 0) but I got no message.

Thank you very much in advance!

Code:

if not server then
  require('socket')
  server = socket.udp()
  server:setsockname('127.0.0.1', 5485)
end

if not tcp then
    tcp = assert(socket.tcp())
    local res, err = tcp:connect('192.168.0.1', 23)
    if res then
      return tcp
    else
      tcp:close()
      return nil, err
    end
end

function denon_receive(tcp)
res, err = tcp:receive()
  if not res then
    return nil, err
  end
   return res
end

while tcp do
  res, err =denon_receive(tcp)
    if res ~= nil then
      log(res,err)
    end
    if (res == nil) then
      log('no response')
    end
end