Rudimentary telnet control over Pioneer AVR Receiver

Code:

--Sends a single telnet command to a host and port
--it returns one line answer
function telnetsend(host, port, command)

  nextline = '\r\n'

  local socket = require("socket")
  local tcp = assert(socket.tcp())
  res, err = tcp:connect(host, port)
  res, err = tcp:send(command .. nextline)
  local answer = tcp:receive('*l')
  tcp:close()
  return answer
end

--Sets the volume to a numeric value
--takes into account, that Pioneer increments the volume in
--2 step intervals. Takes a host ip and port as input.
function setvolume(host, port, volumelevel)

  local currentvolume = getvolume(host, port)

  if volumelevel > currentvolume then
    for i = currentvolume, volumelevel -1, 2 do
      telnetsend(host,port,VOLUME_UP)
    end
  else
    for i = volumelevel, currentvolume-1, 2 do
      telnetsend(host,port,VOLUME_DOWN)
    end
  end
  
  currentvolume = getvolume(host, port)
  return currentvolume

end

--Returns the current volume
function getvolume(host, port)
  
  local currentvolume = tonumber(string.sub(telnetsend(host,port,VOLUME_QUERY), 5))
  return currentvolume
  
end

--Turns reciever on off
function soundonoff(host, port, onoff)
  if onoff == true then
    telnetsend(host,port,POWER_ON)
    local status = telnetsend(host,port,POWER_QUERY)
    if status == POWER_ONSTATE then
      return true
    else
      alert("Could not turn on sound")
    end    
  else
    telnetsend(host,port,POWER_OFF)
    local status = telnetsend(host,port,POWER_QUERY)
    if status == POWER_OFFSTATE then
      return false
    else
      alert("Could not turn off sound")
    end
  end
end

Code:

   -- Main zone
      POWER_ON="PO"
      POWER_OFF="PF"
    POWER_QUERY="?P"
    POWER_ONSTATE="PWR2"
    POWER_OFFSTATE="PWR0"
    
    -- Volume
    VOLUME_UP="VU"
    VOLUME_DOWN="VD"
    VOLUME_QUERY="?V"
    VOLUME_SET="VL"
    
    -- Mute
    MUTE=    "MO"
    UNMUTE=    "MF"
    MUTE_QUERY="?M"

    -- Source / Input channel
    SOURCE_QUERY="?F"
    SOURCE_UP=    "FU"
    SOURCE_DOWN="FD"
    SOURCE_SET=    "%02dFN"
    SOURCE_DVD=    "04FN"
    SOURCE_BD=    "25FN"
    SOURCE_TVSAT="05FN"
    SOURCE_DVR_BDR="15FN"
    SOURCE_VIDEO1="10FN"
    SOURCE_VIDEO2="14FN"
    SOURCE_HDMI1="19FN"
    SOURCE_HDMI2="20FN"
    SOURCE_HDMI3="21FN"
    SOURCE_HDMI4="22FN"
    SOURCE_HDMI5="23FN"
    SOURCE_HMG=    "26FN"
    SOURCE_IPOD_USB="17FN"
    SOURCE_XMRADIO="18FN"
    SOURCE_CD="01FN"
    SOURCE_CDR_TAPE="03FN"
    SOURCE_TUNER="02FN"
    SOURCE_PHONO="00FN"
    SOURCE_MULTICH_IN="12FN"
    SOURCE_ADAPTER_PORT="33FN"
    SOURCE_HDMI_CYCL="31FN"
    
    -- Listening mode
    LISTENING_MODE="%04dSR"
    LISTENING_MODE_QUERY="?L"
    
    -- tone control
    TONE_ON="TO1"
    TONE_BYPASS="TO0"
    TONE_QUERY="?TO"
    
    -- bass control
    BASS_INCREMENT="BI"
    BASS_DECREMENT="BD"
    BASS_QUERY="?BA"
    
    -- treble control
    TREBLE_INCREMENT="TI"
    TREBLE_DECREMENT="TD"
    TREBLE_QUERY="?TR"
    
    -- Speaker configuration
    SPEAKERS="%01dSPK"
    SPEAKERS_OFF="0SPK"
    SPEAKERS_A="1SPK"
    SPEAKERS_B="2SPK"
    SPEAKERS_A_B="3SPK"
    
    -- HDMI outputs configuration
    HDMI_OUTPUT="%01dHO"
    HDMI_OUT_ALL="0HO"
    HDMI_OUT_1="1HO"
    HDMI_OUT_2="2HO"
    
    -- HDMI audio configuration
    HDMI_AUDIO_AMP="0HA"
    HDMI_AUDIO_THROUGH="1HA"
    
    -- PQLS setting
    PQLS_OFF="0PQ"
    PQLS_AUTO="1PQ"
    
    -- Zone 2 control
    ZONE2_POWER_ON=        "APO"
    ZONE2_POWER_OFF="APF"
    ZONE2_POWER_QUERY="?AP"
    ZONE2_INPUT="%02dZS"
    ZONE2_INPUT_DVD="04ZS"
    ZONE2_INPUT_TV_SAT="05ZS"
    ZONE2_INPUT_DVR_BDR="15ZS"
    ZONE2_INPUT_VIDEO1="10ZS"
    ZONE2_INPUT_VIDEO2="14ZS"
    ZONE2_INPUT_HMG="26ZS"
    ZONE2_INPUT_IPOD="17ZS"
    ZONE2_INPUT_XMRADIO="18ZS"
    ZONE2_INPUT_CD=    "01ZS"
    ZONE2_INPUT_CDR_TAPE="03ZS"
    ZONE2_INPUT_TUNER="02ZS"
    ZONE2_INPUT_ADAPTER="33ZS"
    ZONE2_INPUT_SIRIUS="27ZS"
    ZONE2_INPUT_QUERY="?ZS"
    ZONE2_VOLUME_UP="ZU"
    ZONE2_VOLUME_DOWN="ZD"
    ZONE2_VOLUME=    "%02ZV",    "ZV"
    ZONE2_VOLUME_QUERY="?ZV"
    ZONE2_MUTE=        "Z2MO"
    ZONE2_UNMUTE=    "Z2MF"
    ZONE2_MUTE_QUERY="?Z2M"
    
    -- zone 3 control
    ZONE3_POWER_ON=        "BPO"
    ZONE3_POWER_OFF="BPF"
    ZONE3_POWER_QUERY="?BP"
    ZONE3_INPUT="%02dZT"
    ZONE3_INPUT_DVD="04ZT"
    ZONE3_INPUT_TV_SAT="05ZT"
    ZONE3_INPUT_DVR_BDR="15ZT"
    ZONE3_INPUT_VIDEO1="10ZT"
    ZONE3_INPUT_VIDEO2="14ZT"
    ZONE3_INPUT_HMG="26ZT"
    ZONE3_INPUT_IPOD="17ZT"
    ZONE3_INPUT_XMRADIO="18ZT"
    ZONE3_INPUT_CD=    "01ZT"
    ZONE3_INPUT_CDR_TAPE="03ZT"
    ZONE3_INPUT_TUNER="02ZT"
    ZONE3_INPUT_ADAPTER="33ZT"
    ZONE3_INPUT_SIRIUS="27ZT"
    ZONE3_INPUT_QUERY="?ZT"
    ZONE3_VOLUME_UP="YU"
    ZONE3_VOLUME_DOWN="YD"
    ZONE3_VOLUME=    "%02YV"
    ZONE3_VOLUME_QUERY="?YV"
    ZONE3_MUTE=        "Z3MO"
    ZONE3_UNMUTE=    "Z3MF"
    ZONE3_MUTE_QUERY="?Z3M"
    
    -- radio tuner
    TUNER_FREQ_INCREMENT="TFI"
    TUNER_FREQ_DECREMENT="TFD"
    TUNER_FREQ_QUERY_AM="?FR"
    TUNER_FREQ_QUERY_FM="?FR"
    TUNER_BAND=        "TB"
    TUNER_PRESET=    "%01dTP"
    TUNER_CLASS=    "TC"
    TUNER_PRESET_INCREMENT="TPI"
    TUNER_PRESET_DECREMENT="TPD"
    TUNER_PRESET_QUERY="?TP"
    
    -- iPod control
    IPOD_PLAY=            "00IP"
    IPOD_PAUSE=        "01IP"
    IPOD_STOP=            "02IP"
    IPOD_PREVIOS=        "03IP"
    IPOD_NEXT=            "04IP"
    IPOD_REV=            "05IP"
    IPOD_FWD=            "06IP"
    IPOD_REPEAT=        "07IP"
    IPOD_SHUFFLE=        "08IP"
    IPOD_DISPLAY=        "09IP"
    IPOD_CONTROL=        "10IP"
    IPOD_CURSOR_UP=    "13IP"
    IPOD_CURSOR_DOWN="14IP"
    IPOD_CURSOR_LEFT="15IP"
    IPOD_CURSOR_RIGHT="16IP"
    IPOD_ENTER=        "17IP"
    IPOD_RETURN=        "18IP"
    IPOD_TOP_MENU=        "19IP"
    IPOD_KEY_OFF=        "KOF"
    
    ADAPTER_PLAY_PAUSE="20BT"
    ADAPTER_PLAY="10BT"
    ADAPTER_PAUSE="11BT"
    ADAPTER_STOP="12BT"
    ADAPTER_PREVIOUS="13BT"
    ADAPTER_NEXT="14BT"
    ADAPTER_REV="15BT"
    ADAPTER_FWD="16BT"
    
    -- Home Media Gateway (HMG) control
    HMG_NUMKEY="%02dNW"
    HMG_NUMKEY_0="00NW"
    HMG_NUMKEY_1="01NW"
    HMG_NUMKEY_2="02NW"
    HMG_NUMKEY_3="03NW"
    HMG_NUMKEY_4="04NW"
    HMG_NUMKEY_5="05NW"
    HMG_NUMKEY_6="06NW"
    HMG_NUMKEY_7="07NW"
    HMG_NUMKEY_8="08NW"
    HMG_NUMKEY_9="09NW"
    HMG_PLAY="10NW"
    HMG_PAUSE="11NW"
    HMG_PREV="12NW"
    HMG_NEXT="13NW"
    HMG_DISPLAY="18NW"
    HMG_STOP="20NW"
    HMG_UP=    "26NW"
    HMG_DOWN="27NW"
    HMG_RIGHT="28NW"
    HMG_LEFT="29NW"
    HMG_ENTER="30NW"
    HMG_RETURN="31NW"
    HMG_PROGRAM="32NW"
    HMG_CLEAR="33NW"
    HMG_REPEAT="34NW"
    HMG_RANDOM="35NW"
    HMG_MENU="36NW"
    HMG_EDIT="37NW"
    HMG_CLASS="38NW"
    
    -- display info text
    DISPLAY_INFO_QUERY="?FL"