#!/usr/bin/lua

-- Created by jiaqiang.ye@lnxall.com
-- Implementation of 创业惠康 protocol
-- 2022/01/11

-- Load external modules
local uci = require 'uci'
local bit = require 'bit'
local posix = require 'posix'
local mosq = require 'mosq'
local cjson = require 'cjson'
local ubus = require 'ubus'
local struct = require 'struct'
local invoker = require 'invoker'
local cyhkp = require 'cyhkp'
local cyhkthread = require 'cyhkthread'

-- global protocol running information
local cyhk_proto = {}
-- global loop flag
local cyhk_run = true
-- MQTT input handler table
local cyhk_cmdtab = {}
-- system network configure function table
local cyhk_nettab = {}
-- gateway sn
local g_devsn = nil

local function nonzero_string(wstr)
	local typn = type(wstr)
	if typn ~= "string" then return false end
	if string.len(wstr) > 0 then return true end
	return false
end
-- signal handler
local function handle_signal(signo)
    -- set loop flag to false
    cyhk_run = false
end

-- function to initialize CYHK protocol running information
local function cyhk_proto_init(product_key)
    -- setup PATH, procd does not give us `/lib/dyiot/bin
    posix.setenv('PATH',
        '/lib/dyiot/bin:/usr/sbin:/usr/bin:/sbin:/bin', true)
    -- get MAC address of the gateway
    local devinfo, macaddr = cyhkp.factory_get(), nil
    if devinfo then macaddr = devinfo.MAC end
    if not macaddr or #macaddr == 0 then
        io.stderr:write("Error, cannot get the MAC address\n")
        io.stderr:flush()
        return false
    end

    -- get serial-no for gateway
    g_devsn = devinfo.SN
    if type(g_devsn) ~= "string" or string.len(g_devsn) == 0 then
        io.stderr:write("Error, serialno not found for gateway.\n")
        io.stderr:flush()
        return false
    end

    -- set productKey and macaddress to working thread
    if not cyhkthread.setpkey(product_key, macaddr) then
        io.stderr:write("Error, cannot set set productKey for working thread\n")
        return false
    end

    -- Use the upper-case version of MAC address
    macaddr = string.upper(macaddr)
    cyhk_proto.macaddr = macaddr
    -- construct subscription topic
    cyhk_proto.topic = string.format("%s/%s/in/+", product_key, macaddr)

    -- create ubus connection
    cyhk_proto.ucon = ubus.connect()
    if not cyhk_proto.ucon then
        io.stderr:write("Error, failed to connect to ubus\n")
        return false
    end

    -- create MQTT client
    cyhk_proto.mqtt = mosq.new('LNXALL_CYHK', true)

    -- number of times connected
    cyhk_proto.connected = false

    -- successfully registered to cloud
    cyhk_proto.registered = false
    return true
end

local function cyhk_proto_connected(why)
    cyhk_proto.connected = true
    io.stdout:write('MQTT broker connected: ' .. tostring(why) .. "\n")
    io.stdout:flush()
end

local function cyhk_proto_disconnect(why)
    cyhk_proto.connected = false
    cyhkthread.stop() -- stop the working thread
    io.stderr:write("Disconnected from MQTT broker: " .. tostring(why) .. "\n")
end

-- 平台回复心跳
cyhk_cmdtab[cyhkp.CMD_HEARTBEAT_RSP] = function (pmsg)
    io.stdout:write("Received heart-beat reply from cloud.\n")
    io.stdout:flush()
    return false
end

-- 平台回复入网请求
cyhk_cmdtab[cyhkp.CMD_CONNECT_RSP] = function (pmsg)
    if pmsg.result == 0 then
        cyhk_proto.registered = true
        print("Access to cloud has been granted!")
    else
        cyhk_proto.registered = false
        print("Access to cloud has been denied!")
    end
    return false
end

-- 平台发送NTP服务器配置
cyhk_cmdtab[cyhkp.CMD_NTPCFG] = function (pmsg)
    local msgs = pmsg.body
    if type(msgs) == "table" then msgs = msgs[1] end
    if type(msgs) == "table" then msgs = msgs.msg end
    if type(msgs) ~= "table" then
        return nil, "invalid config for NTP setting"
    end

    local host, port = msgs.host, msgs.port
    if type(host) ~= "string" or #host == 0 then return nil, "invalid NTP host ipaddr" end
    if type(port) ~= "number" then return nil, "invalid NTP port number" end
    print(string.format("New NTP Server: %s, port: %d", host, port))

    local ntpcfg = uci.cursor('/etc/config')
    -- update NTP system configuration
    ntpcfg:set('system', 'ntp', 'timeserver')
    ntpcfg:set('system', 'ntp', 'enabled', '1')
    ntpcfg:set('system', 'ntp', 'enable_server', '1')
    ntpcfg:set('system', 'ntp', 'port', tostring(port))
    ntpcfg:set('system', 'ntp', 'server', { [1] = host, } )
    ntpcfg:commit('system') -- save configuration
    ntpcfg = nil

    -- reload sysntpd service.
    os.execute('exec /etc/init.d/sysntpd reload')
    return true
end

-- command: 131
-- function to update WAN configuration
cyhk_nettab[cyhkp.MSGTYPE_NETCFG_WAN] = function (wancfg)
    local iptype = wancfg.ip_type

    local network, wan = 'network', 'wan'
    local netdev = cyhkp.WAN_NETDEV
    local waninfo = cyhk_proto.ucon:call('network.interface.wan', 'status', {})
    if type(waninfo) == "table" and
        type(waninfo.l3_device) == "string" and
        string.len(waninfo.l3_device) > 0 then
        netdev = waninfo.l3_device
    end
    if iptype == 0 then -- dhcp
        -- load configuration from `/etc/config
        local netcfg = uci.cursor('/etc/config')

        netcfg:delete(network, wan) -- delete WAN configuration first
        netcfg:set(network, wan, 'interface')
        netcfg:set(network, wan, 'proto', 'dhcp')
        netcfg:set(network, wan, 'ifname', netdev)
        netcfg:set(network, wan, 'metric', '0')
        netcfg:set(network, wan, 'defaultroute', '1')
        netcfg:commit(network) -- write to /etc/config/network

        netcfg = nil
        return true, cyhkp.POST_RELOAD_NETWORK -- do reload netifd service
    end

    if iptype == 1 then -- static
        -- validate various static IP address settings
        if type(wancfg.gateway) ~= "string" or string.len(wancfg.gateway) == 0 then
            return nil, "invalid gateway for WAN"
        end
        if type(wancfg.ipaddr) ~= "string" or string.len(wancfg.ipaddr) == 0 then
            return nil, "invalid ipaddr for WAN"
        end
        if type(wancfg.netmask) ~= "string" or string.len(wancfg.netmask) == 0 then
            return nil, "invalid netmask for WAN"
        end
        if type(wancfg.dnss) ~= "string" or string.len(wancfg.netmask) == 0 then
            return nil, "invalid dnss for WAN"
        end

        local netcfg = uci.cursor('/etc/config')
        netcfg:delete(network, wan) -- delete previous configuration
        netcfg:set(network, wan, 'interface')
        netcfg:set(network, wan, 'proto', 'static')
        netcfg:set(network, wan, 'ifname', netdev)
        netcfg:set(network, wan, 'gateway', wancfg.gateway)
        netcfg:set(network, wan, 'ipaddr', wancfg.ipaddr)
        netcfg:set(network, wan, 'netmask', wancfg.netmask)

        local dnslst = {}
        for dns in string.gmatch(wancfg.dnss, '%S+') do
            dnslst[#dnslst + 1] = dns
        end
        netcfg:set(network, wan, 'dns', dnslst)
        netcfg:commit(network)

        netcfg = nil
        return true, cyhkp.POST_RELOAD_NETWORK -- do reload netifd service
    end

    -- PPPoE connection support
	if iptype == 2 then
		if type(wancfg.pppoeuser) ~= "string" or string.len(wancfg.pppoeuser) == 0 then
			return nil, "no valid PPPoE username given"
		end
		if type(wancfg.pppoepass) ~= "string" or string.len(wancfg.pppoepass) == 0 then
			return nil, "no valid PPPoE password given"
		end
		local netcfg = uci.cursor('/etc/config')
		netcfg:delete(network, wan) -- remove old configuration
		netcfg:set(network, wan, 'interface')
		netcfg:set(network, wan, 'proto', 'pppoe')
		netcfg:set(network, wan, 'ifname', netdev)
		netcfg:set(network, wan, 'username', wancfg.pppoeuser)
		netcfg:set(network, wan, 'password', wancfg.pppoepass)
		netcfg:commit(network); netcfg = nil
		return true, cyhkp.POST_RELOAD_NETWORK
	end
    return nil, "unknown network configuration for WAN"
end

-- command 131
-- function to update WIFI configuration
cyhk_nettab[cyhkp.MSGTYPE_NETCFG_WIFI] = function (wcfg)
    local vaplist = wcfg.vap_list
    if type(vaplist) ~= "table" then
        return nil, "no WiFi configuration found"
    end
    local idx, haswwan = 0, false
    local cleared, noerror, errmsg = false, true, nil
    local wificfg = uci.cursor('/etc/config')
    while true do
        idx = idx + 1
        -- only support two configurations
        if idx > 2 then break end
        local vap = vaplist[idx]
        if type(vap) ~= "table" then
            if idx == 1 then noerror, errmsg = false, "no WiFi configuration found" end
            break
        end
        if vap.mode ~= "ap" and vap.mode ~= 'sta' then
            noerror, errmsg = false, "invalid WiFi mode"
            break
        end
        local vapn = vap.vap_name
        if type(vapn) ~= "string" or string.len(vapn) == 0 then
            noerror, errmsg = false, "invalid WiFi vap_name"
            break
        end
        if type(vap.ssid) ~= "string" or
            string.len(vap.ssid) == 0 or
            string.len(vap.ssid) >= 31 then
            noerror, errmsg = false, "invalid WiFi ssid, too long or too short"
            break
        end
        if not cleared then
            local ifaces = {}
            wificfg:foreach('wireless', 'wifi-iface', function (ifa) ifaces[#ifaces + 1] = ifa[".name"] end)
            for _, iface in ipairs(ifaces) do wificfg:delete('wireless', iface) end
            ifaces = nil
            cleared = true -- wifi-iface has been cleared
        end

        wificfg:set('wireless', vapn, 'wifi-iface')
        -- radio0: the name of default `wifi-device
        local wdev = type(vap.device) == "string" and vap.device or 'radio0'
        wificfg:set('wireless', wdev, 'disabled', '0')
        wificfg:set('wireless', wdev, 'channel',
            type(vap.channel) == "string" and vap.channel or 'auto')

        wificfg:set('wireless', vapn, 'device', wdev)
        wificfg:set('wireless', vapn, 'mode', vap.mode)
        wificfg:set('wireless', vapn, 'ssid', vap.ssid)
        local haspw = type(vap.key) == "string" and string.len(vap.key) > 0
        if haspw then wificfg:set('wireless', vapn, 'key', vap.key) end
        if vap.mode == "ap" then
            wificfg:set('wireless', vapn, 'network', 'lan')
        else -- station mode
            haswwan = true
            wificfg:set('wireless', vapn, 'network', 'wifiwan')
        end
        wificfg:set('wireless', vapn, 'encryption', haspw and "psk2" or "none")
        wificfg:set('wireless', vapn, 'disabled', vap.disabled and '1' or '0')
    end

    if not noerror then -- something wrong happened
        wificfg = nil
        return nil, errmsg
    end

    if haswwan then
        -- Add wireless wan, delete them first
        wificfg:delete('network', 'wifiwan')
        wificfg:delete('network', 'wifiwan')
        wificfg:set('network', 'wifiwan', 'interface')
        wificfg:set('network', 'wifiwan', 'proto', 'dhcp')
        wificfg:set('network', 'wifiwan', 'metric', '20')
        wificfg:commit('network')
    end

    -- write the configuration files
    wificfg:commit('wireless')
    wificfg = nil
    return true, cyhkp.POST_RELOAD_WIFI
end

-- command 131
-- function to update LAN configuration, static IP configuration only
cyhk_nettab[cyhkp.MSGTYPE_NETCFG_LAN] = function (lancfg)
    -- check various configuration items
    if lancfg.ip_type ~= 1 then
        return nil, "invalid ip_type for LAN"
    end
    if type(lancfg.ipaddr) ~= "string" or string.len(lancfg.ipaddr) == 0 then
        return nil, "invalid ipaddr for LAN"
    end
    if type(lancfg.netmask) ~= "string" or string.len(lancfg.ipaddr) == 0 then
        return nil, "invalid netmask for LAN"
    end
    if lancfg.dhcp_server_enable ~= 0 and lancfg.dhcp_server_enable ~= 1 then
        return nil, "invalid dhcp_server enable option for LAN"
    end
    if type(lancfg.dhcp_start) ~= "number" or
        type(lancfg.dhcp_limit) ~= "number" or
        type(lancfg.dhcp_leasetime) ~= "number" then
        return nil, "invalid DHCP server options for LAN"
    end

    local netdev = nil
    local laninfo = cyhk_proto.ucon:call('network.interface.lan', 'status', {})
    if type(laninfo) == "table" and
        type(laninfo.l3_device) == "string" and
        string.len(laninfo.l3_device) > 0  then
        netdev = laninfo.l3_device
    else
        return nil, "cannot get network device for LAN"
    end
    -- begin to write new configurations
    local netcfg = uci.cursor('/etc/config')
    netcfg:delete('network', 'lan') -- delete old LAN configuration first
    netcfg:set('network', 'lan', 'interface')
    netcfg:set('network', 'lan', 'type', 'bridge')
    netcfg:set('network', 'lan', 'ifname', netdev)
    netcfg:set('network', 'lan', 'proto', 'static')
    netcfg:set('network', 'lan', 'ipaddr', lancfg.ipaddr)
    netcfg:set('network', 'lan', 'netmask', lancfg.netmask)
    netcfg:commit('network')

    netcfg:delete('dhcp', 'lan') -- remove old DHCP configuration for LAN
    netcfg:set('dhcp', 'lan', 'dhcp')
    netcfg:set('dhcp', 'lan', 'interface', 'lan')
    netcfg:set('dhcp', 'lan', 'dhcpv6', 'server')
    netcfg:set('dhcp', 'lan', 'ra', 'server')
    netcfg:set('dhcp', 'lan', 'networkid', netdev)
    netcfg:set('dhcp', 'lan', 'start', tostring(lancfg.dhcp_start))
    netcfg:set('dhcp', 'lan', 'limit', tostring(lancfg.dhcp_limit))
    netcfg:set('dhcp', 'lan', 'leasetime', tostring(lancfg.dhcp_leasetime))
    netcfg:set('dhcp', 'lan', 'force', '1')
    netcfg:set('dhcp', 'lan', 'ignore', '0')
    if lancfg.dhcp_server_enable == 0 then
        netcfg:set('dhcp', 'lan', 'dhcpv4', 'disabled')
        netcfg:set('dhcp', 'lan', 'dhcpv6', 'disabled')
    end

    netcfg:commit('dhcp')
    netcfg = nil
    if lancfg.dhcp_server_enable == 0 then
        invoker.invoke(invoker.CLOSEFD, '/etc/init.d/odhcpd', 'stop', 'disable')
    else
        invoker.invoke(invoker.CLOSEFD, '/etc/init.d/odhcpd', 'enable', 'start')
    end
    return true, cyhkp.POST_RELOAD_NETWORK
end

-- command 131
-- function to update 4G network setting
cyhk_nettab[cyhkp.MSGTYPE_NETCFG_4GLTE] = function (cfg4g)
    if type(cfg4g.APN) ~= "string" or string.len(cfg4g.APN) == 0 then
        return nil, "invalid APN for 4G LTE network"
    end
    -- User name not used
    if type(cfg4g.password) ~= "string" or string.len(cfg4g.password) == 0 then
        return nil, "invalid password for 4G LTE network"
    end
    -- refer to config_manager/src/cm_handle_msg.c, function `msg_set_sim_card,
    -- which invokes shell script: /lib/dyiot/bin/clear_sim_pin_set_apn.sh
    os.execute(string.format('exec /lib/dyiot/bin/clear_sim_pin_set_apn.sh -p %s -a %s',
        cfg4g.password, cfg4g.APN))
    return true, cyhkp.POST_RELOAD_NETWORK
end

-- command 131
-- function to update MQTT server setting
cyhk_nettab[cyhkp.MSGTYPE_NETCFG_MQTT] = function (mcfg)
    if type(mcfg.host) ~= "string" or string.len(mcfg.host) == 0 then
        return nil, "invalid MQTT Server hostname"
    end
    if type(mcfg.port) ~= "number" then
        return nil, "invalid MQTT Server port"
    end
    if type(mcfg.user) ~= "string" then
        return nil, "invalid MQTT Server username"
    end
    if type(mcfg.pass) ~= "string" then
        return nil, "invalid MQTT Server password"
    end
    if not invoker.tcpcheck(mcfg.host, mcfg.port, 2500) then
        return nil, "failed to connect to new MQTT server"
    end

    local cafile, certfile, keyfile = mcfg["cafile"], mcfg["certfile"], mcfg["keyfile"]
    if type(cafile) ~= "string" then cafile = "" end
    if type(certfile) ~= "string" then certfile = "" end
    if type(keyfile) ~= "string" then keyfile = "" end

    -- download TLS related files
    if string.len(cafile) > 0 and not cyhkp.download(cafile, cyhkp.MQTTCA, 0x3, 0x5) then
        return nil, string.format("Error, failed to download '%s'", cafile)
    end
    if string.len(certfile) > 0 and not cyhkp.download(certfile, cyhkp.MQTTCERT, 0x3, 0x5) then
        return nil, string.format("Error, failed to download '%s'", certfile)
    end
    if string.len(keyfile) > 0 and not cyhkp.download(keyfile, cyhkp.MQTTKEY, 0x3, 0x5) then
        return nil, string.format("Error, failed to download '%s'", keyfile)
    end

    -- open /app/config/mqtt_server.json
    local filh = io.open(cyhkp.MQTTSVRCFG, "w")
    if not filh then return false end

    filh:write(string.format('{\n\t"host": "%s",\n\t"port": %d,\n\t"user": "%s",\n\t"pass": "%s",\n\t',
        mcfg.host, mcfg.port, mcfg.user, mcfg.pass))
    filh:write(string.format('"cafile": "%s",\n\t"certfile": "%s",\n\t"keyfile": "%s"\n}\n',
        string.len(cafile) > 0 and cyhkp.MQTTCA or cafile,
        string.len(certfile) > 0 and cyhkp.MQTTCERT or certfile,
        string.len(keyfile) > 0 and cyhkp.MQTTKEY or keyfile))
    filh:close(); filh = nil
    return true, cyhkp.POST_RECONNECT
end

-- 平台下发网络配置
cyhk_cmdtab[cyhkp.CMD_NETCFG] = function (pmsg)
    local msgs = pmsg.body
    if type(msgs) ~= "table" then
        return nil, "Error, invalid config for Network settings"
    end

    local idx, postact = 1, 0
    -- iterate all network settings
    while msgs[idx] do
        local netcfg = msgs[idx]
        local msgnet = netcfg.msg
        local handler = cyhk_nettab[netcfg.msg_type]
        if type(msgnet) ~= "table" or not handler then
            io.stderr:write("Warning, unknown network type, ignored\n")
        else
            local okay, errmsg = handler(msgnet)
            if not okay then return nil, errmsg end
            if type(errmsg) == "number" and
                errmsg > 0 and bit.band(postact, errmsg) == 0 then
                postact = postact + errmsg
            end
        end
        idx = idx + 1 -- next network config
    end
    return true, postact
end

-- function to get WAN/LAN information
local function wanlan_info(wanlan)
    -- Get WAN/LAN working status
    local wlinfo = cyhk_proto.ucon:call('network.interface.' .. wanlan, 'status', {})
    if type(wlinfo) ~= "table" then
        io.stderr:write("Error, cannot get status for WAN!\n")
        return nil
    end
    -- construct reply message for WAN/LAN
    local wl_info = { proto = wlinfo.proto, status = wlinfo.up and '1' or '0' }
    -- store IPv4 address information
    local ipaddr = wlinfo["ipv4-address"]
    if type(ipaddr) == "table" and ipaddr[1] then
        ipaddr = ipaddr[1]
        wl_info.subnet = string.format("%s/%d", ipaddr.address, ipaddr.mask)
    end
    -- store DNS settings for WAN/LAN
    local dnss = wlinfo["dns-server"]
    if type(dnss) == "table" and
        type(dnss[1]) == "string" and
        string.len(dnss[1]) > 0 then
        wl_info.dnss = table.concat(dnss, " ")
    end
    -- read from /sys/class/net/{NETDEV}/...
    local netdev = wlinfo.l3_device
    if type(netdev) == "string" and
        posix.access(string.format("/sys/class/net/%s/address", netdev)) then
        local dirpath = '/sys/class/net/' .. netdev
        wl_info.macaddr = invoker.readfile(dirpath .. '/address', invoker.TRIMEND)
        wl_info.speed = invoker.readfile(dirpath .. '/speed', invoker.TRIMEND)
        wl_info.txbytes = invoker.readfile(dirpath .. '/statistics/tx_bytes', invoker.TRIMEND)
        wl_info.rxbytes = invoker.readfile(dirpath .. '/statistics/rx_bytes', invoker.TRIMEND)
        wl_info.txpackets = invoker.readfile(dirpath .. '/statistics/tx_packets',
            invoker.TRIMEND)
        wl_info.rxpackets = invoker.readfile(dirpath .. '/statistics/rx_packets',
            invoker.TRIMEND)
    end
    return wl_info
end

-- 平台请求网络信息
cyhk_cmdtab[cyhkp.CMD_NETSTATUS] = function (pmsg)
    local wan_info = wanlan_info('wan')
    local lan_info = wanlan_info('lan')

    local wcount, wifi_info = 0, {}
    local wifi = cyhk_proto.ucon:call('network.wireless', 'status', {})
    if type(wifi) == "table" then
        -- iterate the radio devices
        for wdev, wst in pairs(wifi) do
            local wcfg = type(wst) == "table" and wst["config"] or nil
            if type(wcfg) ~= "table" then
                io.stderr:write("Error, cannot get config for " .. wdev .. "\n")
                break
            end
            -- get the radio device path
            local devpath = string.format('/sys/devices/%s',
                type(wcfg.path) == "string" and wcfg.path or "NONEXIST")
            if posix.access(devpath) then
                local wifiup = false
                local radinfo, first_wifi = {}, nil
                -- get only the first configuration
                if type(wst["interfaces"]) == "table" and
                    type(wst["interfaces"][1]) == "table" and
                    type(wst["interfaces"][1]["config"]) == "table" then
                    wifiup = true
                    first_wifi = wst.interfaces[1].config
                else
                    local ifaces, wificfg = {}, uci.cursor('/etc/config')
                    wificfg:foreach('wireless', 'wifi-iface',
                        function (ifa) ifaces[#ifaces + 1] = ifa[".name"] end)
                    first_wifi = ifaces[1] and ifaces[1] or {}
                    wificfg = nil
                end
                radinfo["radio"]       = wdev
                radinfo["type"]        = first_wifi.mode
                radinfo["up"]          = wifiup
                radinfo["channel"]     = wcfg.channel
                radinfo["ssid"]        = first_wifi.ssid
                radinfo["encryption"]  = first_wifi.encryption

                wcount = wcount + 1
                wifi_info[wcount] = radinfo
                first_wifi = nil
            end
        end
    end

    -- load 4G LTE information
    local lteinfo = nil
    local tty4g = invoker.readfile('/tmp/4g_modem_tty', invoker.TRIMEND)
    if tty4g and #tty4g > 0 and posix.access(tty4g) then -- 4G LTE device found
        lteinfo = {}
        lteinfo.IMEI = invoker.readfile('/tmp/simcard_imei', invoker.TRIMEND)
        lteinfo.IMSI = invoker.readfile('/tmp/simcard_imsi', invoker.TRIMEND)
        lteinfo.REG = invoker.readfile('/tmp/simcard_reg', invoker.TRIMEND)
        -- Get signal strength
        local _, sig4g = invoker.invoke(invoker.OUTPUT + invoker.CLOSEFD, 'gcom',
            '-s', '/etc/gcom/getstrength.gcom', '-d', tty4g)
        if sig4g and #sig4g > 0 then
            lteinfo.SIG = string.match(sig4g, 'CSQ:%s+([%d,]+)')
        end
    end

    -- load MQTT configuration
    local mqttcfg = cyhkp.load_mqtt_svrcfg()
    if type(mqttcfg) == "table" then
        -- remove sensitive fields
        mqttcfg.user = nil; mqttcfg.pass = nil
        mqttcfg.cafile = nil; mqttcfg.certfile = nil
        mqttcfg.keyfile = nil
    end

    local netcnt = 0
    local reply = {}
    if wan_info then
        netcnt = netcnt + 1
        reply[netcnt] = { msg_type = 31, msg = wan_info } -- WAN
    end
    if wcount > 0 then
        netcnt = netcnt + 1
        reply[netcnt] = { msg_type = 32, msg = wifi_info } -- WiFi
    end
    if lan_info then
        netcnt = netcnt + 1
        reply[netcnt] = { msg_type = 33, msg = lan_info } -- LAN
    end
    if lteinfo then
        netcnt = netcnt + 1
        reply[netcnt] = { msg_type = 34, msg = lteinfo } -- 4G Network
    end
    if mqttcfg then
        netcnt = netcnt + 1
        reply[netcnt] = { msg_type = 35, msg = { host = mqttcfg.host,
            port = mqttcfg.port, state = cyhk_proto.connected and 1 or 0, } }
    end

    return true, reply
end

-- 平台下发升级请求
cyhk_cmdtab[cyhkp.CMD_FWUPGRADE] = function (pmsg)
    local upmsg, url = nil, nil
    -- Get firmware URL for download
    if type(pmsg.body) == "table" then upmsg = pmsg.body[1] end
    if type(upmsg) == "table" then upmsg = upmsg.msg end
    if type(upmsg) == "table" then url = upmsg.url end
    if type(url) ~= "string" or #url == 0 then
        return nil, "no valid firmware download url found"
    end

    -- check firmware size, mininum: 16 bytes, maximum: 512MB
    local fsize = upmsg.size
    if type(fsize) ~= "number" or fsize <= 0x10 or fsize > 0x20000000 then
        return nil, "no invalid firmware size found"
    end

    -- check firmware md5sum
    local md5sum = upmsg.md5
    if type(md5sum) ~= "string" or #md5sum ~= 32 then
        return nil, "no valid md5sum found for firmware"
    end

    local dlsize, errmsg = cyhkp.download(url,
        cyhkp.FWPATH, true, nil, fsize, md5sum)
    if dlsize ~= fsize then
        posix.unlink(cyhkp.FWPATH)
        if type(errmsg) ~= "string" then errmsg = "unknown download error" end
        return nil, errmsg
    end
    io.stdout:write("Firmware downloaded successfully!\n")
    io.stdout:flush()
    return true, cyhkp.POST_FWUPGRADE
end

-- 平台下发重启
cyhk_cmdtab[cyhkp.CMD_REBOOT] = function (pmsg)
    return true, cyhkp.POST_REBOOT
end

-- function to process templates_cfg.json and nodes_cfg.json
local function handle_template_node(tptcfg, nodcfg)
    -- load templates_cfg.json configuration
    local odtempcfg = cyhkp.load_json_config(cyhkp.TEMPLATECFG, nil)
    if not odtempcfg or type(odtempcfg.template_cfg) ~= "table" then
        io.stderr:write("Warning, using empty templates_cfg.json!\n")
        odtempcfg = {}; odtempcfg.template_cfg = {}
    end
    -- load nodes_cfg.json configuration
    local odnodecfg = cyhkp.load_json_config(cyhkp.NODECFG, nil)
    if not odnodecfg or type(odnodecfg.nodes_cfg) ~= "table" then
        io.stderr:write("Warning, using empty nodes_cfg.json!\n")
        odnodecfg = {}; odnodecfg.nodes_cfg = {}
    end

    local idx = 0
    -- nodes_cfg.json and templates_cfg.json are not modified:
    local mod_nodcfg, mod_temcfg = false, false
    -- add or remove items from templates_cfg.json
    while true do
        idx = idx + 1
        local tcfg = tptcfg and tptcfg[idx] or nil
        if tcfg == nil then break end
        if type(tcfg) ~= "table" then return nil, "invalid type of template item" end

        local tempid = tcfg.template_id
        -- make sure that template_id is a string
        if type(tempid) ~= "string" or #tempid == 0 then return nil, "invalid template_id" end

        -- find the action for the template item
        local action = tcfg.action
        if action ~= "add" and action ~= "remove" then
            return nil, "invalid action for template"
        end

        -- try to find corresponding device/node-config
        local jdx = cyhkp.find_index(nodcfg, 'template_id', tempid)
        if not jdx then return nil, "no corresponding device setting found" end
        local ncfg = nodcfg[jdx]
        -- the actions must be the same, add/remove
        if action ~= ncfg.action then -- action cannot be change here
            return nil, "actions do not match in template and device settings"
        end

        local odncfg, odtcfg = odnodecfg.nodes_cfg, odtempcfg.template_cfg
        -- find the index for `template_id in nodes_cfg.json and templates_cfg.json
        local nodeIdx = cyhkp.find_index(odncfg, "template_id", tempid)
        local tempIdx = cyhkp.find_index(odtcfg, "template_id", tempid)
        if (nodeIdx and type(nodeIdx) ~= "number") or
            (tempIdx and type(tempIdx) ~= "number") then
            return nil, "Error, invalid index type for template or node items"
        end

        if action == "add" then
            -- remove `action field
            ncfg.action = nil; tcfg.action = nil
            -- As a workaround for BLE nodes_cfg.json configuration,
            -- if the node_cfg item does not have `ext_data field,
            -- encode itself as JSON string and insert it as `ext_data
            if ncfg.ext_data == nil then
                local extd = cjson.encode(ncfg)
                ncfg["ext_data"] = extd; extd = nil
            end
            mod_nodcfg, mod_temcfg = true, true
            if nodeIdx then odncfg[nodeIdx] = ncfg
            else odncfg[#odncfg + 1] = ncfg end
            if tempIdx then odtcfg[tempIdx] = tcfg
            else odtcfg[#odtcfg + 1] = tcfg end
        else -- remove the configuration
            if nodeIdx then
                while true do
                    local nextcfg = odncfg[nodeIdx + 1]
                    odncfg[nodeIdx] = nextcfg
                    if nextcfg == nil then break end
                    nodeIdx = nodeIdx + 1; nextcfg = nil
                end
                mod_nodcfg = true
            end
            if tempIdx then
                while true do
                    local nextcfg = odtcfg[tempIdx + 1]
                    odtcfg[tempIdx] = nextcfg
                    if nextcfg == nil then break end
                    tempIdx = tempIdx + 1; nextcfg = nil
                end
                mod_temcfg = true
            end
        end -- action == remove
    end -- while true do

    idx = 0
    -- modify nodes_cfg.json
    while true do
        idx = idx + 1
        local ncfg = nodcfg[idx]
        if ncfg == nil then break end
        if type(ncfg) ~= "table" then return nil, "invalid type of device-node item" end
        local action = ncfg.action
        if type(action) == "string" then
            local tempid = ncfg.template_id
            if type(tempid) ~= "string" then return nil, "invalid template-id for node item" end
            if action == "change" then -- here we only process items that has changed
                local jdx = cyhkp.find_index(odnodecfg.nodes_cfg, 'template_id', tempid)
                if not jdx then
                    io.stderr:write("Warning, template_id not found: " .. tempid .. "\n")
                    -- return nil, "device-node cannot be changed, template_id: " .. tempid
                else
                    mod_nodcfg = true; ncfg.action = nil
                    if ncfg.ext_data == nil then
                        local extd = cjson.encode(ncfg)
                        ncfg["ext_data"] = extd; extd = nil
                    end
                    odnodecfg.nodes_cfg[jdx] = ncfg
                end
            else -- action ~= "change"
                io.stdout:write(string.format("Action '%s' ignored for %s\n", action, tempid))
                io.stdout:flush()
            end
        end -- type(action) == "string"; note that action might be nil, see above
    end

    -- OK, we're now done:
    if mod_nodcfg then cyhkp.write_json_config(cyhkp.NODECFG, odnodecfg) end
    if mod_temcfg then cyhkp.write_json_config(cyhkp.TEMPLATECFG, odtempcfg) end
    odnodecfg = nil; odtempcfg = nil -- explicitly set the tables to nil
    return true
end

-- function to process card information
local function handle_cardinfo(cinfo)
    local scfgm = false
    -- load rs485 port cfg file
    local serialcfg = cyhkp.load_json_config(cyhkp.RS485PORTCFG)
    if not serialcfg or type(serialcfg["rs485_cfg"]) ~= "table" then
        scfgm = true
        serialcfg = {} -- empty RS485 serial configuration
        local rs485_cfg = {}
        rs485_cfg[1] = {}; rs485_cfg[2] = {}
        rs485_cfg[3] = {}; rs485_cfg[4] = {}
        serialcfg.rs485_cfg = rs485_cfg
    end
    for _, cardi in ipairs(cinfo) do
        -- check the type of elements
        if type(cardi) ~= "table" then
            return nil, "invalid card information settings"
        end
        -- check the type of `card_id
        local cardid, proto = cardi.card_id, cardi.protocol
        print("type(cardid == %s)" .. type(cardid))
        print("type(cardid) == %s" .. type(proto))
        if type(cardid) ~= "number" or type(proto) ~= "number" then
            return nil, "invalid type of card_id or protocol"
        end
        -- check again, valid values for `card_id: 0, 1, 2, 3
        if cardid < 0 or cardid >= 4 or
            cardid ~= math.floor(cardid) then
            return nil, "invalid card_id, not in range"
        end

        -- check card interface
        local iface = cardi.interface
        if iface == "SERIAL" and type(cardi.serial_cfg) == "table" then
            scfgm = true -- need to write to cyhkp.RS485PORTCFG
            serialcfg.rs485_cfg[cardid + 1] = cardi.serial_cfg
        end

        -- check cfg fild
        local ccfg = cardi.cfg
        if type(ccfg) ~= "table" then
            return nil, string.format("cfg not given for card_id: %d", cardid)
        end
        local cfgfile, errmsg = cyhkp.cardinfo_path(cardid, proto)
        if not cfgfile then return nil, errmsg end
        cyhkp.write_json_config(cfgfile, ccfg)
    end

    if scfgm then cyhkp.write_json_config(cyhkp.RS485PORTCFG, serialcfg) end
    return true
end

-- function to process application installation
local function handle_appinst(appinfo)
    local idx, acnt = 0, 0
    while true do -- loop: install applications one-by-one
        idx = idx + 1
        local ipkg = appinfo[idx]
        if ipkg == nil then break end
        if type(ipkg) ~= "table" then return nil, "invalid application install information" end
        local action = ipkg.action
        if action ~= "add" and action ~= "change" and action ~= "remove" then
            return nil, "invalid action for application"
        end
        local appn = ipkg.name -- application name
        if type(appn) ~= "string" or string.len(appn) == 0 then
            return nil, "invalid application name"
        end
        if action == "remove" then
            local exst, obuf = invoker.invoke(invoker.OUTPUT + invoker.TRIMEND +
                invoker.CLOSEFD, cyhkp.opkg, "remove", appn)
            if exst ~= 0 then
                return nil, "failed to remove package: " .. appn
            end
            if obuf and #obuf > 0 then print(obuf) end
        else
            local pkgurl = ipkg.URL
            if type(pkgurl) ~= "string" or #pkgurl == 0 then
                return nil, "URL not given for package: " .. appn
            end
            -- extract package full name:
            local pkgname = string.match(pkgurl, '([^/]+)$')
            if not pkgname or #pkgname == 0 then
                return nil, "invalid URL for application install"
            end
            -- get md5sum
            local pkgmd5 = ipkg.md5sum
            if type(pkgmd5) ~= "string" or #pkgmd5 ~= 32 then
                return nil, "invalid package md5sum given"
            end

            -- download installation package first
            local dlpath = "/tmp/" .. pkgname
            local okay, errmsg = cyhkp.download(pkgurl, dlpath, true, nil, false, pkgmd5)
            if not okay then return nil, errmsg end

            -- reinstall the package, remove first
            if action == "change" then
                local exst = invoker.invoke(invoker.NOSTDIO + invoker.CLOSEFD,
                    cyhkp.opkg, "remove", appn)
                if exst ~= 0 then return nil, "failed to remove package: " .. appn end
            end

            -- invoke /bin/opkg with reinstall forced
            okay = invoker.invoke(invoker.CLOSEFD,
                cyhkp.opkg, "--force-reinstall", "install", dlpath)
            posix.unlink(dlpath)
            if okay ~= 0 then return nil, "failed to install package: " .. appn end
            io.stdout:write("Installed package successfully: " .. pkgname .. "\n")
        end
        acnt = acnt + 1
    end

    if acnt == 0 then return nil, "no package removed or installed" end
    return true
end

-- 平台下发运行参数配置
cyhk_cmdtab[cyhkp.CMD_PARAMS] = function (pmsg)
    local msgs = pmsg.body
    if type(msgs) ~= "table" then
        return nil, "no parameters found"
    end
    local ncount = 0
    local cardcfg = nil -- 插卡配置
    local tempcfg = nil -- 模版配置
    local devcfg = nil  -- 设备修改
    local appcfg = nil  -- 应用安装

    for _, cfgval in pairs(msgs) do
        if type(cfgval) ~= "table" then
            return nil, "invalid parameter settings"
        else
            local mtype = cfgval.msg_type
            if mtype == cyhkp.MSGTYPE_PARAM_CARD then
                if cardcfg then return nil, "Card settings given more than once" end
                cardcfg = cfgval.msg
                if type(cardcfg) ~= "table" then return nil, "invalid card settings" end
            elseif mtype == cyhkp.MSGTYPE_PARAM_TEMPLATE then
                if tempcfg then return nil, "Template settings given more than once" end
                tempcfg = cfgval.msg
                if type(tempcfg) ~= "table" then return nil, "invalid template settings" end
            elseif mtype == cyhkp.MSGTYPE_PARAM_DEVICE then
                if devcfg then return nil, "Device settings given more than once" end
                devcfg = cfgval.msg
                if type(devcfg) ~= "table" then return nil, "invalid device settings" end
            elseif mtype == cyhkp.MSGTYPE_PARAM_APPINST then
                if appcfg then return nil, "Application settings given more than once" end
                appcfg = cfgval.msg
                if type(appcfg) ~= "table" then return nil, "invalid application settings" end
            else
                return nil, "Unknown msg_type for parameter settings"
            end
            ncount = ncount + 0x1
        end
    end
    if ncount == 0 then return nil, "No parameter settings found" end
    print("Number of configurations found: " .. tostring(ncount))

    local okay, errmsg = nil, nil
    -- handle card configuration
    if cardcfg then
        okay, errmsg = handle_cardinfo(cardcfg)
        if not okay then return nil, errmsg end
    end

    -- template settings and
    if devcfg then
        okay, errmsg = handle_template_node(tempcfg, devcfg)
        if not okay then return nil, errmsg end
    end

    -- handle application installation
    if appcfg then
        okay, errmsg = handle_appinst(appcfg)
        if not okay then return nil, errmsg end
    end
    return true, cyhkp.POST_RELOAD_SERVICES
end

-- 数据通信 - 平台回复或平台下发数据
cyhk_cmdtab[cyhkp.CMD_DATA_REPLY] = function (pmsg)
    local msgs = pmsg["body"]
    local typn = type(msgs)
    if typn ~= "table" then
        return nil, "Invalid data body"
    end
    local idx, errs = 0, 0
    while true do
        idx = idx + 1
        local msg = msgs[idx]
        typn = type(msg)
        if typn == "table" then
            msg = msg["msg"]
            typn = type(msg)
        end
        if typn ~= "table" then break end

        local devsn = msg["sn"]
        typn = type(devsn)
        if typn == "string" and string.len(devsn) > 0 then
            local devport = "BLE" -- default BLE device
            local topic = string.format("ipc/%s/%s/device/%s/data/Set_Rglt",
                g_devsn, devport, devsn)
            if not cyhkthread.pubint(topic, cjson.encode(msg)) then
                errs = errs + 1
            end
        end
    end
    if errs == 0 then return true end
    return nil, string.format("Failed to forward message, erros: %d\n", errs)
end

-- 平台请求 - 网关运行状态
cyhk_cmdtab[cyhkp.CMD_STATUS_REQ] = function (pmsg)
    local mem, cpu, temp, disk = nil, nil, nil, nil

    -- get memory usage and cpu load
    local exitst, topinfo = invoker.invoke(invoker.OUTPUT + invoker.CLOSEFD,
        'top', '-n', '1', '-d', '1')
    if exitst == 0 and topinfo and string.len(topinfo) > 0 then
        local memused, memfree = string.match(topinfo, 'Mem:%s+(%d+)K used,%s+(%d+)K free')
        if memused and memfree then
            memused = tonumber(memused)
            memfree = tonumber(memfree)
            mem = math.floor(memused * 100 / (memused + memfree))
        end
        local cpuusr, cpusys = string.match(topinfo, 'CPU:%s+(%d+)%%%s+usr%s+(%d+)%%')
        if cpuusr and cpusys then
            cpu = tonumber(cpuusr) + tonumber(cpusys)
        end
    end

    -- compute the average cpu temperature
    local temps, cpuidx = 0, 0
    while true do
        local tfile = string.format("/sys/class/thermal/thermal_zone%d/temp", cpuidx)
        local tmp = invoker.readfile(tfile, invoker.TRIMEND)
        if not tmp or #tmp == 0 then break end
        tmp = tonumber(tmp)
        if tmp then temps = temps + tmp end
        cpuidx = cpuidx + 1
    end
    if cpuidx > 0 then temp = math.floor(temps / cpuidx) end

    -- call `df -h` is much simpler
    local dfh = io.popen("exec busybox df -h")
    if not dfh then return nil, "failed to get disk usage" end
    for line in dfh:lines() do
        local pinfo = {}
        for part in string.gmatch(line, '(%S+)') do
            pinfo[#pinfo + 1] = part
        end
        if pinfo[6] == "/" then
            disk = pinfo[5]
            break
        end
    end
    -- close pipe file handle
    dfh:close(); dfh = nil

    local replyMsg = {mem = mem, cpu = cpu, temp = temp, disk = disk}
    return true, replyMsg
end

-- function to parse the CYHK MQTT message
local function cyhk_proto_parse(topin, pmsg)
    local cmdval = string.match(topin, '/(%d+)$')
    if cmdval then cmdval = tonumber(cmdval) end
    if not cmdval then
        io.stderr:write("invalid topic, no command found: " .. topin .. "\n")
        return nil
    end

    -- check whether the command is available
    if not cyhk_cmdtab[cmdval] then
        io.stderr:write("unknown CYHK command from cloud: " .. tostring(cmdval) .. "\n")
        return nil
    end

    local plen = string.len(pmsg)
    -- check against length of CYHK magic
    if plen < 0x4 then return nil end -- sliently drop the message
    -- unpack the magics
    local serial_id, st_class, st_id = struct.unpack('BB>H', pmsg:sub(1, 0x4))
    if serial_id ~= 100 then -- 100 -> JSON data
        io.stderr:write(string.format("invalid serialization ID: 0x%x\n", serial_id))
        return nil
    end

    -- parse the json data, which must be present
    local okay, jdat = false, nil
    if plen > 0x4 then okay, jdat = pcall(cjson.decode, pmsg:sub(0x5)) end
    if not okay then
        io.stderr:write(tostring(jdat))
        io.stderr:write("failed to decode JSON data:\n")
	io.stderr:write(pmsg:sub(0x5))
	io.stderr:write("\n")
        return nil
    end

    local header = jdat.header
    local typn = type(header)
    if typn ~= "table" then
        io.stderr:write(string.format(string.format("invalid header type: %s\n", typn)))
        return nil
    end

    -- check the msgid
    typn = type(header.id)
    if typn ~= "number" and typn ~= "string" then
        io.stderr:write(string.format("invalid message-id, type: %s\n", typn))
        return nil
    end

    local rval = {}
    rval.command = cmdval
    rval.serialid = serial_id
    rval.structclass = st_class
    rval.structid = st_id
    rval.id = header.id
    rval.result = header.result
    typn = type(jdat.body)
    if typn == "string" and string.len(jdat.body) > 0 then
        okay, rval.body = pcall(cjson.decode, jdat.body)
        if not okay then
            io.stderr:write("Error, invalid body string!\n")
            io.stderr:flush()
            return nil
        end
    else
        rval.body = {} -- empty body
    end

    -- set jdat to nil, for the good of garbage collector
    header.id = nil
    header.result = nil
    header = nil
    jdat.header = nil
    jdat.result = nil
    jdat.body = nil
    jdat = nil
    return rval
end

-- function to publish MQTT messages
local function cyhk_publish_message(topic, tabmsg)
    local serial_id = 100
    local struct_class = 50
    local struct_id = 11582
    local payload = struct.pack('BB>H', serial_id, struct_class, struct_id)
    if type(tabmsg) == "table" then
        payload = payload .. cjson.encode(tabmsg)
    else -- tabmsg must be a string
        payload = payload .. tabmsg
    end
    cyhkthread.publish(topic, payload)
end

-- function to handle MQTT incoming messages
local function cyhk_proto_recvmsg(mid, topicin, cyhkmsg)
    local msg = cyhk_proto_parse(topicin, cyhkmsg)
    if not msg then return false end

    local cmdv = msg.command
    print("Topic:         " .. topicin)
    print("command:       " .. tostring(cmdv))
    print("struct class:  " .. tostring(msg.structclass))
    print("struct id:     " .. tostring(msg.structid))

    -- We've checked that the command handler exists
    local rval, postact = cyhk_cmdtab[cmdv](msg)
    if rval == nil then
        if type(postact) == "string" then io.stderr:write(postact .. "\n") end
        -- reply with an error message, postact must be a string
        local tval = cyhkp.CMDRSP[cmdv] or 0
        local topic = string.format('%s/%s/out/%d', cyhkp.PRODUCTKEY,
            cyhk_proto.macaddr, tval)
        tval = cyhkp.STRUCTIDS[tval] or 0
        local errmsg = { ["header"] = { id = msg.id, result = 1,
            reason = postact, structId = tval }, ["body"] = "", }
        cyhk_publish_message(topic, errmsg)
    elseif rval then
        -- reply with a success reply
        local tval = cyhkp.CMDRSP[cmdv] or 0
        local topic = string.format('%s/%s/out/%d', cyhkp.PRODUCTKEY,
            cyhk_proto.macaddr, tval)
        local body, typn = nil, type(postact)
        if typn == "table" then
            body = cjson.encode(postact)
        elseif typn == "string" then
            body = postact
        end
        tval = cyhkp.STRUCTIDS[tval] or 0
        local response = { ["header"] = { id = msg.id, result = 0, structId = tval },
            ["body"] = body or "", }
        cyhk_publish_message(topic, response)
    else
        io.stdout:write("No need to reply command: " .. tostring(cmdv) .. "\n")
    end
    if type(postact) == "number" and postact ~= 0 then
        if bit.band(postact, cyhkp.POST_RELOAD_WIFI) ~= 0 then
            invoker.invoke(invoker.CLOSEFD, 'wifi', 'reload')
        end
        if bit.band(postact, cyhkp.POST_RELOAD_NETWORK) ~= 0 then
            posix.nanosleep{tv_sec = 1, tv_nsec = 500000000} -- delay 1.5 second
            cyhk_proto.ucon:call('network', 'reload', {})
        end
        if bit.band(postact, cyhkp.POST_RELOAD_FIREWALL) ~= 0 then
            invoker.invoke(invoker.CLOSEFD, '/etc/init.d/firewall', 'reload')
        end
        if bit.band(postact, cyhkp.POST_RELOAD_DNSMASQ) ~= 0 then
            invoker.invoke(invoker.CLOSEFD, '/etc/init.d/dnsmasq', 'reload')
        end
        if bit.band(postact, cyhkp.POST_FWUPGRADE) ~= 0 then
            posix.nanosleep{tv_sec = 1, tv_nsec = 500000000} -- delay 1.5 second
            invoker.invoke(invoker.NOSTDIO + invoker.CLOSEFD,
                '/sbin/sysupgrade', '-F', cyhkp.FWPATH)
        end
        if bit.band(postact, cyhkp.POST_REBOOT) ~= 0 then
            posix.nanosleep{tv_sec = 1, tv_nsec = 500000000} -- delay 1.5 second
            posix.sync() -- flush filesystem
            -- invoker.invoke(0, 'reboot')
            cyhk_proto.ucon:call('system', 'reboot', {})
        end
        if bit.band(postact, cyhkp.POST_RELOAD_SERVICES) ~= 0 then
            -- need to reload a list of services
            cyhkp.reloadservices()
        end
        if bit.band(postact, cyhkp.POST_RECONNECT) ~= 0 then
            posix.nanosleep{tv_sec = 1, tv_nsec = 500000000} -- delay 1.5 second
            cyhk_proto.mqtt:disconnect()
            io.stdout:write("Old MQTT broker disconnected!\n")
            io.stdout:flush()
        end
    end

    -- destroy msg, for the good of garbage collector
    msg.command = nil
    msg.serialid = nil
    msg.structclass = nil
    msg.structid = nil
    msg.id = nil
    msg.result = nil
    msg.body = nil
    return true
end

-- function to connect and subscribe MQTT topic
local function cyhk_proto_connect()
    -- load MQTT broker configuration
    local brkcfg = cyhkp.load_mqtt_svrcfg(nil)
    cyhkthread.setaddr(brkcfg.host, brkcfg.port, brkcfg.user,
        brkcfg.pass) -- update the configuration for working thread

    local mqtt = cyhk_proto.mqtt
    -- determine TLS related files
    local cafile, certfile, keyfile = brkcfg["cafile"], brkcfg["certfile"], brkcfg["keyfile"]
    if not nonzero_string(cafile) then cafile = nil end
    if not nonzero_string(certfile) then certfile = nil end
    if not nonzero_string(keyfile) then keyfile = nil end
    if cafile or certfile or keyfile then
        local certs = true
        local okay = mqtt:tls_set(cafile, nil, certfile, keyfile)
        if okay and not certfile and not keyfile then certs = false end
        if okay then okay = mqtt:tls_opts_set(certs, "tlsv1.2") end
        if not okay then
            io.stderr:write("Error, failed to set MQTT TLS options!\n")
            io.stderr:flush()
            return false
        end
    end

    if type(brkcfg.user) == "string" and string.len(brkcfg.user) > 0 then
        if not mqtt:login_set(brkcfg.user, brkcfg.pass) then
            io.stderr:write("Failed to set MQTT broker username/password\n")
            io.stderr:flush()
            return false
        end
    end

    -- register message callback function
    mqtt.ON_CONNECT = cyhk_proto_connected
    mqtt.ON_MESSAGE = cyhk_proto_recvmsg
    -- register disconnect callback function
    mqtt.ON_DISCONNECT = cyhk_proto_disconnect

    local retv, errmsg = mqtt:connect(brkcfg.host, brkcfg.port)
    if not retv then
        io.stderr:write("Failed to connect MQTT broker: " .. tostring(errmsg) .. "\n")
        io.stderr:write(string.format("MQTT broker host: %s, port: %d\n",
            brkcfg.host, brkcfg.port))
        io.stderr:flush()
        return false
    end
    -- underlying TCP connection might be established later
    cyhk_proto.connected = true

    -- subscribe main topic
    retv = mqtt:subscribe(cyhk_proto.topic)
    if not retv then
        io.stderr:write(string.format("Error, failed to subscribe topic: %s\n",
            cyhk_proto.topic))
        return false
    end

    local mosq_ptr = mqtt:get_handle()
    if type(mosq_ptr) ~= "string" then
        io.stderr:write("Error, unknown type of handle!\n");
        io.stderr:flush()
        return false
    end

    -- start working thread first
    if not cyhkthread.start(mosq_ptr) then
        io.stderr:write("Error, cannot start working thread!\n")
        return false
    end
    return true
end

-- LNXALL-CYHK protocol main function.
-- MQTT connection has been established, and topic subscribed.
local function cyhk_proto_main()
    local devinfo = cyhkp.factory_get()
    if not devinfo then devinfo = {} end -- empty table
    -- construct registration message
    local body = { [1] = { ["msg_type"] = 1, ["msg"] = {
            ["hard_ver"] = devinfo.HWVER,
            ["firm_ver"] = devinfo.FIRMVER,
            ["spec_ver"] = cyhkp.VERSION,
            ["module_ver"] = devinfo.PRODUCT, },
        }
    }
    local regmsg = {
        ["header"] = { id = cyhkthread.msgid(), result = 0,
            structId = cyhkp.STRUCTIDS[cyhkp.CMD_CONNECT] },
        ["body"] = cjson.encode(body),
    }

    local regtop = string.format('%s/%s/out/%d',
        cyhkp.PRODUCTKEY, cyhk_proto.macaddr, cyhkp.CMD_CONNECT)

    local tnow, thet = invoker.uptime(), nil
    local count, mqtt = 0, cyhk_proto.mqtt
    io.stdout:write("Trying to register to CYHK cloud...\n"); io.stdout:flush()
    -- wait until registered to cloud
    while not cyhk_proto["registered"] do
        if count < 2 then
            count = count + 1
            cyhk_publish_message(regtop, regmsg)
        end
        thet = invoker.uptime()
        -- registration timeout in 30 seconds:
        if (thet - tnow) >= 30 then
            io.stderr:write("Failed to register to cloud!\n")
            io.stderr:flush()
            return false
        end
        mqtt:loop(3000)
        if not cyhk_run then break end
    end

    -- free memory by settings unused variables to nil
    regmsg = nil; devinfo = nil; regtop = nil

    -- OK, now we have registered to cloud
    tnow = invoker.uptime()
    while cyhk_proto["connected"] do
        if not cyhk_run then break end
        thet = invoker.uptime()
        -- send hearbeat every 55 seconds
        if (thet - tnow) >= 55 then
            tnow = tnow + 55 -- update heartbeat timestamp
            local topic = string.format("%s/%s/out/%d", cyhkp.PRODUCTKEY,
                cyhk_proto.macaddr, cyhkp.CMD_HEARTBEAT)
            local hmsg = { ["header"] = { id = cyhkthread.msgid(),
                structId = cyhkp.STRUCTIDS[cyhkp.CMD_HEARTBEAT] }, ["body"] = "", }
            cyhk_publish_message(topic, hmsg)
        end
        -- loop for 5 seconds
        if not mqtt:loop(5000) then
            io.stderr:write("MQTT loop has failed, and don't known why\n")
            -- cannot break here
        end
    end
end

posix.chdir("/")
mosq.init() -- initialize MQTT library
invoker.setname('cyhkp') -- set process name
posix.signal(posix.SIGINT, handle_signal)

if not cyhk_proto_init(cyhkp.PRODUCTKEY) then os.exit(1) end
-- set SIGCHLD handler to default,
-- so that child processes have to be waited:
posix.signal(posix.SIGCHLD, posix.SIG_DFL)

-- connect and receive messages
if cyhk_proto_connect() then cyhk_proto_main() end

io.stdout:write("CYHK protocol application exits!\n")
cyhkthread.stop()
-- destroy MQTT connection
cyhk_proto.mqtt:destroy()
cyhk_proto.mqtt = nil
-- destroy ubus connection
cyhk_proto.ucon:close()
cyhk_proto.ucon = nil
os.exit(2) -- terminate script gracefully