why connection succese in jvm and fail with responseCode 400 in android project

Question

I try this code in Idea and it work very well. but when I pack it as jar and import to another android porject, it fail. I am a green hand and don't know much. What is the different between them and how I can fix it?

fun getSourceCode(url: URL, encode: String = "UTF-8"): String {
    var contentBuffer: StringBuffer? = StringBuffer()
    val responseCode: Int
    var con: HttpURLConnection? = null
    try {
        con = url.openConnection() as HttpURLConnection
        con.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)")
        con.connectTimeout = 60000
        con.readTimeout = 60000
        
        responseCode = con.responseCode
        if (responseCode == -1) {
            con.disconnect()
            throw Exception("connect fail")
        }
        
        if (responseCode >= 400) {
            con.disconnect()
            throw Exception("connect fail, responseCode: $responseCode")
        }
        val inStr: InputStream = con.inputStream
        val iStreamReader = InputStreamReader(inStr, encode)
        val buffStr = BufferedReader(iStreamReader)
        var str: String?
        while (buffStr.readLine().also { str = it } != null) contentBuffer!!.append(str)
        inStr.close()
    } catch (e: IOException) {
        e.printStackTrace()
        contentBuffer = null
        println("error: $url")
    } finally {
        con?.disconnect()
    }
    return contentBuffer.toString()
}