How to force Java to use IPv4 instead IPv6?

Question

My Java browser plug-in is no longer working. When I open a page that has a Java element, Java cannot connect to the server.

After investigation, I found that Java was trying to use IPv6, while my network does not support IPv6, so Java always fails to connect.

I tried looking on Google and found that I should run Java with -Djava.net.preferIPv4Stack=true, but how can I pass this to the browser?

I use Google Chrome and Java 7 update 5.

Why don't you disable the IPv6 protocol so Java won't have this option. — harrymc, Aug 30 '13 at 18:55
it is a old story, I do not know if I've disable IPv6 protocol, seems to have, I've forgotten, what I remember is I remove Java 7 and replace it with Java 6 — nyongrand, Aug 31 '13 at 09:21
@javadba: Links are never dead : see the Wayback Machine, but it's outdated. Better google "Disable IPv6 On Windows" for half a million results. — harrymc, Jan 16 '17 at 07:31
It does not get passed the the browser it is used when the app starts. — mckenzm, Nov 23 '23 at 22:52

score 90 · Accepted Answer · answered Jul 25 '12 at 10:33

90

Put the options in _JAVA_OPTIONS environment variable. How to do this is already described in various other posts – although they usually talk about setting PATH, but it's all the same.

For example, on Linux, put the following in your ~/.profile or ~/.bash_profile:

export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true"

answered Jul 25 '12 at 10:33

u1686_grawity

452,512

1

ok, thanks for your reply, although i use windows but your solution inspire me, thanks – nyongrand Jul 25 '12 at 19:28
1

See for example this post for setting environment variables: http://superuser.com/questions/284342/what-are-path-and-other-environment-variables-and-how-can-i-set-or-use-them – user2428118 Aug 30 '13 at 18:12
1

Why does Java 'prefer' IPV6? It seems to break code that was working. – Ribo Apr 02 '16 at 15:18
How to set it in Windows ? – Adnan Ali Jun 18 '17 at 09:51
1

@Ribo: By default, Java uses dual-stack IPv6 when possible, that is, it uses IPv6 sockets that also support IPv4 addresses. These sockets are still compatible with IPv4 applications by using IPv4-mapped addresses. Therefore, this is a backward-compatible behavior. – Dr. Koutheir Attouchi Aug 24 '17 at 08:38
IPv4-mapped addresses break proxies. – MarcH Dec 05 '18 at 00:44

score 0 · Answer 2 · answered Mar 23 '21 at 17:08

0

when launching from the command line, add parameter:

-Djava.net.preferIPv4Stack=true

ie:

java -jar -Djava.net.preferIPv4Stack=true some.jar

answered Mar 23 '21 at 17:08

alex

1

The environment variable mentioned in the other answer will also work, though, and is recommended over environments where the java cmd isn't directly accessible – OneCricketeer Sep 06 '23 at 18:49

How to force Java to use IPv4 instead IPv6?

2 Answers2