Wireshark lua script for capturing audio/mpeg content

script.lua

-- tshark -i tap0 -Xlua_script:./script.lua  -f "src port 80" -O HTTP > /dev/null

function lastfile()
    local max = 0
    for filename in io.popen("ls data/*.mp3"):lines() do

        local curr = tonumber(string.sub(filename, filename:find("%d+")))
        if curr > max then
            max = curr
        end
    end
    return max
end

function install_listener()
    local http_media_f = Field.new("media")

    local tap = Listener.new(nil, 'tcp.srcport == 80 && http.content_type == "audio/mpeg" && media')
    local i = lastfile()
    function tap.packet(pinfo,tvb)
        local http_media = http_media_f()

        i = i+1
        local fn = "data/"..tostring(i)..".mp3"
        local file = io.open(fn, "wb")
        file:write(http_media.value:tvb()():string())
        file:close()
        io.stderr:write("dumped to "..fn.."\n")
    end
end

install_listener()