invalid IPv6 address

Question

I got the Error Message:

Error occurs in downloading files from ftp Server : ftp://speedtest.tele2.net: invalid IPv6 address

from this lines:

String serverAddress = "ftp://speedtest.tele2.net";
FTPClient ftp = new FTPClient();
ftp.connect(serverAddress);

I dont got a clue what to do about that?

The only advices i got are about this System Propertys, but that didnt solved the problem.

java.net.preferIPv4Stack -> true
java.net.preferIPv6Addresses -> true

Anyone got Advices or Refereces? Thank you very much!

Yes, i tried `System.setProperty("java.net.preferIPv6Addresses", "false");` but it didnt helped. — AbsolutBeginner, Oct 25 '16 at 12:28

score 8 · Accepted Answer · answered Oct 25 '16 at 12:34

8

The site has both IPv6 and IPv4 addresses

$ dig AAAA speedtest.tele2.net -> 2a00:800:1010::1
$ dig A speedtest.tele2.net    -> 90.130.70.73

IPv6 is usually preferred if available. But while the server can be reached at the IPv4 address port 21 it cannot be reached at the IPv6 address, i.e. a inconsistent setup of FTP and DNS.

The error message from Java is confusing since it is actually not the IPv6 address which is bad but it fails to connect to this address.

answered Oct 25 '16 at 12:34

Steffen Ullrich

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Thank you for this clarification! It works with the ip addresses. – AbsolutBeginner Oct 25 '16 at 13:08
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And if possible contact the admin of that server to tell them their setup is broken :) – Sander Steffann Oct 25 '16 at 13:17

score 6 · Answer 2 · answered Oct 25 '19 at 12:27

6

Try to use address without "ftp://"

String serverAddress = "speedtest.tele2.net";

answered Oct 25 '19 at 12:27

Salvador One

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score 0 · Answer 3 · edited Oct 25 '16 at 21:00

0

This probably won't work, setting that property from code.

Have you tried setting the property as a command line argument when running the program:

java -Djava.net.preferIPv6Addresses=false -Djava.net.preferIPv4Stack=true -jar program.jar

edited Oct 25 '16 at 21:00

Ori Dar

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answered Oct 25 '16 at 12:31

Richard Smith

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Asking the OP if they did something sounds more like a comment than an answer. Consider rephrasing "Have you tried setting..." to "Try setting" or something similar – jonhopkins Oct 25 '16 at 12:35

invalid IPv6 address

3 Answers3