srv:listen 出现内存不足错误

我在网上搜索了很久都没有找到答案。 我想在 NodeMCU 上设置一个 wifi AP 和一个 Web 服务器。

我使用以下代码:

wifi.setmode(wifi.STATIONAP)
wifi.ap.config({ ssid = "test", pwd = "12345678" })
print("Server IP Address:", wifi.ap.getip())

srv = net.createServer(net.TCP)
srv:listen(80, function(conn)
    conn:on("receive", function(sck, request)
        print("received: " .. request)
        sck:send("echo: " .. request)
    end)
end)

上传后我得到了以下结果:

> dofile("init.lua");
Server IP Address:  192.168.1.1 255.255.255.0   192.168.1.1
init.lua:6: out of memory
stack traceback:
    [C]: in function 'listen'
    init.lua:6: in main chunk
    [C]: in function 'dofile'
    stdin:1: in main chunk

我使用的固件版本为:

NodeMCU custom build by frightanic.com
    branch: master
    commit: c708828bbe853764b9de58fb8113a70f5a24002d
    SSL: false
    modules: file,gpio,net,node,tmr,uart,wifi
 build created on 2018-11-05 22:20
 powered by Lua 5.1.4 on SDK 2.2.1(6ab97e9)

请问如何解决这个问题？