====== HTTP request implemention using custom protocol ======
The following example sends a HTTP string template to the TCP port upon the register change in the custom protocol. 
Once the response comes, is is copied in the //response// global variable which is returned to the system with the **readRegister** function.

<code lua>
get_example = [[
GET /api/register-values HTTP/1.1
Host: 127.0.0.1
X-WH-APIKEY:5D78CB6F0B0ACC526F2CB8BF65B471A2E594D309
X-WH-CONNECTIONS:  1
Accept: application/json
Content-Type: application/json
]]
response = "no data"

function createDevices ()
  addDevice({name = "S",  shift = 0, base = 10, xtraFields = {}})
end

function onScanStart ()
  -- no actions on scan start 
end

function readRegister (reg, device, unitId)
  return response
end

function writeRegister (reg, device, unitId, newValue)

   sendString(get_example .. "\n")        

   local s = read_string() 
   
   if (not s) or (#s == 0) then 
       return false 
   else 
       response = s              -- copy response to global 
       return true 
   end 

end

function read_string()
    local str = {}
    
    repeat 
        local char_ = readString(1)
        if char_ then 
            -- DEBUG("Read char = " .. char_)
            table.insert(str, char_) 
        end 
    until not char_
    local response = table.concat(str)
    DEBUG("read_string going to return " .. response)
    return response
end 

</code>

===== How to change request parameters  =====

When you want to dynamically change your request paramters, the above example could be further extended to this verstion: 

<code lua>
GET_TEMPLATE = { getPath = "GET /api/registers/" , 
                 reg = 611,  -- can be modified from outside 
                 getTail =  " HTTP/1.1" .. "\r\n", 
                 acceptHeader = "Accept: application/json".."\r\n", 
                --  host = "Host: 192.168.1.110".."\r\n", 
                 host = "Host: 127.0.0.1".."\r\n", 
                 apiKey = "X-WH-APIKEY: 4025D32205ADC52E8604690FFADFB4600B8D41AA".."\r\n", 
                 endLine = "\r\n"
                 
}

function GET_TEMPLATE : make() 
    local newRequest =   self.getPath 
                      .. self.reg 
                      .. self.getTail 
                      
                      .. self.acceptHeader 
                      .. self.host 
                      .. self.apiKey 
                      .. self.endLine 
    
    return newRequest
end 

function createDevices ()
    addDevice{name = "CMD",  shift = 0, base = 10, xtraFields = {} };
end

function readRegister (reg, device, unitId)
  return status_ 
end

function writeRegister (reg, device, unitId, newValue)
    
    -- check for zero 
    if (newValue == 0) then 
        status_ = false 
        return true              -- no GET will be done 
    else 
        GET_TEMPLATE.reg = newValue -- change target  for request 
    end 
    
    sendString_(GET_TEMPLATE : make() )
    
    local response_ = readAll()
    
    if (#response_ > 0) then 
        DEBUG("got something ... " .. response_)
        status_ = 1 
    else 
        status_ = false 
    end 
    
    return true 
end

------------------ Helpers ---------------

-- new sendString version 
function sendString_(s)
                                                DEBUG("Going to send: " .. s)
    local sendBuf = {} 
    
    for i = 1, #s do 
        table.insert(sendBuf, s : byte(i) )
    end 
    sendBytes(sendBuf)
    
end

-- read everything that is in buffer 
function readAll()
    local rbuf = {}
    repeat 
            local b = readString(1)
            if b then 
                table.insert(rbuf, b)
            end 
    until (not b)

    return table.concat(rbuf)
end 

------------ Not in use ------------------  
function onScanStart ()
end


</code>