TLSv1弃用后HTTPS文件传输失效，sendString配置求助

核心问题 #

1. 错误使用POST请求：Dropbox带dl=1参数的下载链接是通过GET请求直接获取文件的，不需要发送请求体，当前代码误用POST方法，还试图设置无关的请求体参数sendString，这是连接重置的关键原因。
2. sendString未定义：代码引用了未声明的sendString变量，会直接抛出错误；同时POST请求对应的content-type、content-length请求头以及source参数都是多余配置。
3. 响应处理逻辑不一致：配置了sink = ltn12.sink.table(response_body)将响应写入表，但后续仍试图用response变量写入文件，会导致文件内容异常。

修复后的代码 #

--downloadfile - downloads a file to the gateway
--Returns:
--result - result of this function
--filename - name of file
--fulllocalpath - path where file is stored locally
--resultstr - status info
local function downloadfile(filename, url, isbinary)
    local string1 = " Downloading file from: " .. url
    --print("UMONIoT","INFO", string1)

    -- retrieve the content of a URL
    local rawname = url
    local fname = filename  --rawname:match("[%w+.%w]+$")
    local fulllocalpath = FTPATH .. fname

    log("UMONIoT","INFO", "Starting download to local directory: " .. fulllocalpath)
    local resultstr = "Starting download to local directory: " .. fulllocalpath .."\r" 

    local response_body = {}
    local response, resultcode, respheaders, respstatus

    if rawname:match("https://") then
        local https = require'ssl.https'
        local ltn12 = require("ltn12") -- 显式导入ltn12库

        -- 使用GET请求，配置TLSv1.2（或v1.3）
        response, resultcode, respheaders, respstatus = https.request{
            url = rawname,
            protocol = 'tlsv1_2', -- 若ssl库支持，可改为'tlsv1_3'
            method = 'GET', -- 改为GET请求
            sink = ltn12.sink.table(response_body) -- 将响应写入response_body表
        }

        log("UMONIoT","INFO", "File download response [" .. tostring(response) .. "].")
        log("UMONIoT","INFO", "File download resultcode [" .. tostring(resultcode) .. "].")
        log("UMONIoT","INFO", "File download respstatus [" .. tostring(respstatus) .. "].")
        -- 将response_body表拼接成字符串，用于后续写入文件
        response = table.concat(response_body)
    else
        local http = require("socket.http")
        response, resultcode = http.request(url)
    end

    if resultcode ~= 200 then
        log("UMONIoT","ERROR", "Failed to download file. Error code [" .. tostring(resultcode) .. "].")
        resultstr = resultstr .. "Failed to download file. Error code [" .. tostring(resultcode) .. "]."
        return false, nil, nil, resultstr
    else
        -- save the content to a file
        if isbinary == true then
            local f = assert(io.open(fulllocalpath, 'wb')) -- open in "binary" mode
            f:write(response)
            f:close()
        else
            local f = assert(io.open(fulllocalpath, 'w'))
            if fname:match("SETUP") then
                local newresponse = updateIPandCredentials(response)
                f:write(newresponse)
                f:close()
            else
                f:write(response)
                f:close()
            end
        end
        log("UMONIoT","INFO", "Successfully downloaded file: " .. fname .. " to gateway.")
        resultstr = resultstr .. "Successfully downloaded file: " .. fname .. " to gateway."
        return true, filename ,fulllocalpath, resultstr
    end
end

关键调整说明 #

• 请求方法改为GET，移除所有与请求体相关的冗余配置。
• 显式导入ltn12库，避免隐式依赖导致的运行错误。
• 将response_body表拼接为字符串，保证后续写入文件的内容正确。
• 可选：若使用的ssl库支持TLSv1.3，可将protocol参数改为'tlsv1_3'。

内容的提问来源于stack exchange，提问作者Terry Z.