java - Too many connections in url openstream

Question

im trying here at first check, if the file on URL exists and then if it exists download it. But it throws me

Exception in thread "main" sun.net.ftp.FtpProtocolException: Welcome message: 421 Too many connections (2) from this IP

If i know, i always close the connection, but anyway it crashes

private boolean exists(String URLName) throws MalformedURLException, IOException {
    boolean result = false;
        URL url = new URL(URLName);
        input = url.openStream();
        input.close();
        result = true;  
    return result;
}

private void downloadTheFile(String path, String name) throws MalformedURLException, IOException {
    input.close();
    input = new URL(path).openStream();
    try {
    OutputStream out = new FileOutputStream(name + ".pdf");
        byte buf[] = new byte[4096];
        for (int n = input.read(buf); n > 0; n = input.read(buf)) {
            out.write(buf, 0, n);
        }
    } finally {
        out.close();
        input.close();
    }
}

could anyone help me please?

Answer 1

服务器发现您正在创建太多不同的连接，并立即将您启动。不要为每个文件创建单独的连接。

虽然我不知道您是如何调用下载函数的，但请考虑通过Apache Commons::net使用持久连接。

Answer 2

摆脱 exists() 方法。如果文件不存在，下载方法将失败。仅此一项就会将您的连接减少一半。