Make a secret IR-camera security raspberry pi unit

The script has the typical ping-pong-function already installed, that means if you send ping to the client running on the script, it will send you a pong back. You can do this for hours… 🙂

If you want a reaction to different words you have to add some if-statements.

With some few words more this can get quite confusing. And you can not combine words or commands. The command has to be send as programmed. If you would send “Ping” instead of “ping” nothing would happen, because this is not the same word and the message text is compared with == to the string “ping”.

Another possibility to find command-words in the message is to do this:

functionsnamen = { "help", "time" , "clock", "pid", "temp", "ping",
                    "start", "stop", "uptime" }
functionen = { sendhelp, sendtime, sendtime, sendpid, sendtemperature, sendping,
                startsecuritycam , stopsecuritycam, senduptime }

function checkforcommand( TOID, FROMID )
  for i, name in pairs(functionsnamen) do
    --print( i.." "..name)
    if ( string.find(string.lower(commandstringarray[1]) , name ) ) then
      --print("Command: "..name.." found.")
      functionen[i]( TOID, FROMID, commandstringarray )
      return
    end
  end
end

— in lua means comment. For the two lines above you can remove the comments and see what happens inside the function.

The checkforcommand is called from within the on_msg_receive with this:

if (msg.to.id == our_id) then
    checkforcommand( msg.from.print_name , msg.from.id ) 
end

There are two arrays, one for the command to send called “functionsnamen” and the other one for the functions in the lua-script that are called in case one command is found.

With the string.lower() we convert the commandstringarray[1] to lower case and compare it to functionsnamen. This way it makes no difference if we write “Ping” or “pINg” or “PiNG” or anything like that.

You might have noticed that there is the commandstringarray. This has the following function: After receiveing a message, the complete text is parsed into this array. This way I can check if the first word of the message was “ping” and the second was something else and so on.The commandstringarray is an array of strings. Lua is quite easy with the variable-types and array-types.

To get the message into this array I wrote this function, which is obviously called before checkforcommand:

commandstringarray = {}

function messagetextinstringarray(msg)
  commandstringarray = {}
  leerzeichen = 1
  count = 1
  completestring = msg.text
  -- print( "checkfunction called: msg.text ist: "..completestring )
  leerzeichen = ( string.find(completestring, "%s" ) )
  while leerzeichen ~= nil do
      commandstringarray[count] = string.sub(completestring, 1, leerzeichen )
      -- print("a space found. Partstring: "..commandstringarray[count])
      completestring = string.sub(completestring, leerzeichen + 1 )
      count = count + 1  
      leerzeichen = ( string.find(completestring, "%s" ) )
  end
  commandstringarray[count] = completestring
end

the loop is looking for a space ” ” separating two words and writes the partstrings to subsequent indexes of the array.