LuaSocket - 尝试调用 'try' 字段（为 nil 值）

平台: (Lua和LuaSocket被移植到哪里) 使用ARM 7开发板的嵌入式系统，运行第三方RTOS和TCP/IP协议栈。

已经实现的功能:

• 使用Lua标准库，如"io"调用、print、assert等
• 通过udp = assert（socket.udp）方法发送UDP数据包，assert（udp:send(something))

问题: 执行smtp Lua脚本示例时的错误:

local smtp = require("socket.smtp")
from = "myEmail"
rcpt = {"<someOne's Email>"}
mesgt = { heasers = {someHeader}, body = "Hello World" }
r, e = smtp.send {
    from = from,
    rcpt = rcpt,
    source = smtp.message(mesgt),
    server = "someServer",
    port = 25,
}

-- an error returns after execution:
-- lua\socket\smtp.lua:115: attempt to call field 'try' (a nil value)

-- Corresponding code in smtp.lua around line 115:

function open(server, port, create)
    local tp = socket.try(tp.connect(server or SERVER, port or PORT,
        TIMEOUT, create))
    local s = base.setmetatable({tp = tp}, metat)
    -- make sure tp is closed if we get an exception
    s.try = socket.newtry(function()
        s:close()
    end)
    return s
end

// Where try = newtry() in socket.lua and the corresponding C code is the same
// from the one provided with the library for UNIX:
static int global_newtry(lua_State *L) {
    lua_settop(L, 1);
    if (lua_isnil(L, 1)) lua_pushcfunction(L, do_nothing);
    lua_pushcclosure(L, finalize, 1);
    return 1;
}