A Lua code to measure the latency from an Openwrt router and send this value to the Ubidots Cloud.

ubidots_ping.lua

#!usr/bin/env lua

-- Loading main configuration
local config = require "config"

-- Library to read command output
local io = require "io"

-- Load the http module
local http = require "socket.http"

-- loading ltn12 and json libraries from luci framework
local ltn12 = require "luci.ltn12"
local json = require "luci.json"
local host = string.format("http://%s:%d", config.host, config.port or 80)

-- Getting the retrieved token

for var_id, var_ip in pairs(config.variables) do
  print(var_id, var_ip)
  local f = io.popen(string.format('ping -c 1 -W 4 %s | grep ttl', var_ip))
  local l = f:read("*a")
  f:close()
  local rtime = '-1'
  if l ~= '' then
    -- Getting response time from ping output.
    rtime = string.match(l, "time=(%d+\.%d*)")
  end
  print(rtime)

  local dtime = string.format('{"value": %s}', rtime)
  print(dtime)

  -- Post value to retrieved variable
  local rsp, code, tr = http.request{
    url=string.format("%s/api/v1.6/variables/%s/values/", host, var_id),
    method = "POST",
    headers = {
      ['X-Auth-Token'] = config.token,
      ['Content-Type'] = "application/json",
      ['Content-Length'] = string.len(dtime)
    },
    redirect = true,
    source = ltn12.source.string(dtime),
    sink = ltn12.sink.file(io.stdout)
  }
end