import sun.net.ftp.FtpClient; //导入依赖的package包/类
public static void main(String[] args) throws Exception {
    try (FtpServer server = new FtpServer();
         FtpClient client = FtpClient.create()) {
        (new Thread(server)).start();
        int port = server.getPort();
        client.connect(new InetSocketAddress("localhost", port));
        client.nameList(null);
    } finally {
        if (commandHasArgs) {
            throw new RuntimeException("Test failed. NLST shouldn't have " +
                    "args if nameList parameter is null");
        }
    }
}
 

import sun.net.ftp.FtpClient; //导入依赖的package包/类
/**
 * Gets the <code>Permission</code> associated with the host & port.
 *
 * @return  The <code>Permission</code> object.
 */
@Override
public Permission getPermission() {
    if (permission == null) {
        int urlport = url.getPort();
        urlport = urlport < 0 ? FtpClient.defaultPort() : urlport;
        String urlhost = this.host + ":" + urlport;
        permission = new SocketPermission(urlhost, "connect");
    }
    return permission;
}
 

import sun.net.ftp.FtpClient; //导入依赖的package包/类
FtpInputStream(FtpClient cl, InputStream fd) {
    super(new BufferedInputStream(fd));
    ftp = cl;
}
 

import sun.net.ftp.FtpClient; //导入依赖的package包/类
FtpOutputStream(FtpClient cl, OutputStream fd) {
    super(fd);
    ftp = cl;
}