To access the WebHMI DB data via API, you have to generate API key in the setup menu and use it in your requests. You can use localhost address as a part of the resource address.

function getMeterData(startTime, endTime) 
 
    local c = cURL.easy_init()
    c : setopt{ url = 'http://127.0.0.1/api/meters-log/',
              timeout = 15, 
              httpheader = { 'X-WH-APIKEY: 4025D32205ADC52E8604690FFADFB4600B8D41AA',
                             'X-WH-START: ' .. startTime, 
                             'X-WH-END: ' ..   endTime, 
 
                             'Accept: application/json',
                             'Content-Type: application/json'
                            }
         }
 
    local res = ""
    c:perform{writefunction = function(str)
            res = res .. str
        end}
    c : close()
 
    if (res == '') or (res == '%[%]')then 
        ERROR('No data in response!') 
        return false 
    else 
        DEBUG(res)
        return res 
    end
 
end

function getGraphData(regId, startTime, endTime) 
 
    local c = cURL.easy_init()
    c : setopt{ url = 'http://127.0.0.1/api/graph-data/',
              timeout = 15, 
               httpheader = {'X-WH-APIKEY: 9833A5C553C5E05D944C28615EB252A6CB2E9322',
                             'X-WH-START: ' .. startTime, 
                             'X-WH-END: ' ..   endTime, 
                             'X-WH-SLICES: ' ..   30, 
                             'X-WH-REGISTERS: ' ..   regId, 
 
                             'Accept: application/json',
                             'Content-Type: application/json'
                            }
         }
 
    local res = ""
    c:perform{writefunction = function(str)
            res = res .. str
        end}
    c : close()
 
    if (res == '') or (res == '%[%]')then 
        ERROR('No data in response!') 
        return false 
    else 
        return res 
    end
 
end