實現思路

寫兩個指令碼：
- 第一個指令碼為啟動時執行的常駐指令碼，監聽 CUSTOM 事件的 conference::maintenance 子事件，該子事件有兩個action：conference-create與conference-destroy，通過這兩個action記錄會議數量和會議名稱。
- 第二個指令碼為呼叫時執行指令碼，呼叫時判斷會議數量是否達到最大，如果達到最大，則判斷該呼叫的會議名稱是否為已存在的會議名稱，若不是，則該呼叫將超出會議最大數量，結束通話；若是，則應答。

實現細節

• 因為要在兩個指令碼中共享資料，因此先新增幾個全域性變數，在 vars.xml 中新增以下全域性變數,分別記錄當前會議數量，允許的最多會議數量，以及會議名稱：

<X-PRE-PROCESS cmd="set" data="conference_count=0"/>
<X-PRE-PROCESS cmd="set" data="max_conference_count=1"/>
<X-PRE-PROCESS cmd="set" data="conference_names="/>

• 在 /scripts 目錄新建 conference_listen.lua，用來監聽會議數量和會議名稱的變化：

con = freeswitch.EventConsumer("CUSTOM")
api = freeswitch.API()
for
 
 e in (function() return con:pop(1) end) do
    event_name = e:getHeader("Event-Name")
    event_subclass = e:getHeader("Event-Subclass")
    action = e:getHeader("Action")
--  freeswitch.consoleLog("info", "event\n" .. e:serialize("xml"))
    local conference_name = e:getHeader("Conference-Name")
    local
 
 conference_names = api:executeString("global_getvar conference_names")
    if (event_name == "CUSTOM" and event_subclass == "conference::maintenance") then
        if (action == "conference-create") then
            local conference_count = tonumber(api:executeString("global_getvar conference_count"))
            conference_count = conference_count + 1
            freeswitch.consoleLog("INFO", "New conference created, now there are " .. conference_count .. " conferences\n")
            api:executeString("global_setvar conference_count=" .. conference_count)
            local nFind = string.find(conference_names, conference_name, 1)
            if not nFind then
                conference_names = conference_names .. conference_name .. ";"
                api:executeString("global_setvar conference_names=" .. conference_names)
            end
            freeswitch.consoleLog("info", "Current conference names: " .. conference_names .. "\n")
        elseif (action == "conference-destroy") then
            local conference_count = tonumber(api:executeString("global_getvar conference_count"))
            conference_count = conference_count - 1
            freeswitch.consoleLog("INFO", "Conference destroyed, now there are " .. conference_count .. " conferences\n")
            api:executeString("global_setvar conference_count=" .. conference_count)
            local nFind = string.find(conference_names, conference_name, 1)
            if nFind then
                local new_conference_names = ""
                if nFind ~= 1 then
                    new_conference_names = new_conference_names .. string.sub(conference_names, 1, nFind - 1)
                end
                if nFind ~= string.len(conference_names) - string.len(conference_name) then
                    new_conference_names = new_conference_names .. string.sub(conference_names, nFind + string.len(conference_name) + 1)
                end
                api:executeString("global_setvar conference_names=" .. new_conference_names)
                freeswitch.consoleLog("info", "Current conference names: " .. new_conference_names .. "\n")
            else
                freeswitch.consoleLog("error", "Can not find the conference named: " .. conference_name)
            end

        end
    end
end

• 由於需要啟動FreeSWITCH時啟動該指令碼，因此在 /conf/autoload_configs/lua.conf.xml 中新增一行：
  <param name="startup-script" value="conference_listen.lua"/>
• 在 /scripts 目錄新建指令碼 conference.lua：

api = freeswitch.API()
local conference_count = tonumber(api:executeString("global_getvar conference_count"))
local max_conference_count = tonumber(api:executeString("global_getvar max_conference_count"))
freeswitch.consoleLog("info", "current count: " .. conference_count .. " and max count: " .. max_conference_count)
function answer_conference()
    session:answer()
    session:execute("set", "conference_member_flags=vmute")
    session:execute("conference", argv[1] .. "@video-mcu-stereo")
end
if conference_count < max_conference_count then
    answer_conference()
else
    local conference_names = api:executeString("global_getvar conference_names")
    freeswitch.consoleLog("info", "Current conference names: " .. conference_names .. "\n")
    freeswitch.consoleLog("info", "Conference to find : " .. argv[1])
    local nFind = string.find(conference_names, argv[1], 1)
    if not nFind then
        freeswitch.consoleLog("info", "Too many conferences, hangup!\n")
        local event = freeswitch.Event("CUSTOM", "conference::maintenance")
        event:addHeader("Hangup-Reason", "Too many conferences")
        event:addHeader("Calling-Number", argv[1])
        event:fire()
        session:hangup()
    else
        answer_conference()
    end
end 

• 最後修改撥號計劃，conf/dialplan/default.xml，使指令碼得以執行。

<extension name="cdquality_conferences">
    <condition field="destination_number" expression="^(35\d{2})$">
        <action application="lua" data="conference.lua $1"/>
    </condition>
</extension>