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How to set java.net.preferIPv4Stack=true at runtime?

I need to disable IPv6. For that the java documentation indicates setting jvm property java.net.preferIPv4Stack=true.

But I don't understand how to do it from the code itself.

Many forums demonstrated doing it from the command prompt, but I need to do it at runtime.

Why IPv6 use colon as delimiter instead of dot? [closed]

I cannot find the reason why IPv6 use colon as delimiter instead of dot.
When address is described with port number, it seems clumsy to me.

[2001:db8:85a3:8d3:1319:8a2e:370:7348]:443

What justify using colon?

iPhone/iPad/OSX: How to get my IP address programmatically?

I would like to obtain my iPad's IP address programmatically. How can I query the networking subsystem to find out what my IPv4 (and IPv6) addresses are?

Thanks. PS: Can I disable IPv6 somehow?

How to support both IPv4 and IPv6 connections

I'm currently working on a UDP socket application and I need to build in support so that IPV4 and IPV6 connections can send packets to a server.

I was hoping that someone could help me out and point me in the right direction; the majority of the documentation that I found was not complete. It'd also be helpful if you could point out any differences between Winsock and BSD sockets.

Thanks in advance!

How to store IPv6-compatible address in a relational database

How do I do that?

Right now, IPv6 will not be used, but I need to design the application to make it IPv6-ready. It is necessary to store IP addresses and CIDR blocks (also BGP NLRI, but this is another story) in a MySQL database. I've alway used an INT for IPv4 + a TINYINT for masklen, but IPv6 is 128 bit.

What approach will be best for that? 2xBIGINT? CHAR(16) for binary storage? CHAR(39) for text storage? 8xSMALLINT in a dedicated table?

What would you recommend?

REMOTE_ADDR and IPv6 in PHP

Is it safe to assume that $_SERVER['REMOTE_ADDR'] always returns a IPv4 address?

Thanks!

When is the hybrid IP notation ::ffff:192.168.1.4 appropriate?

Put another way, if an address is IPv4, why bother to express it as IPv6 at all?

IIS Request.UserHostAddress returning IPV6 (::1), even when IPV6 disabled

In the properties section of my network card, on windows server 2008, i have IPV6 disabled, leaving only IPV4 enabled.

However in ASP.NET, Request.UserHostAddress returns '::1', an IPV6 address.

Has anyone got any idea how to revert back to IPV4?

How can I disable IPv6 stack use for IPv4 IPs on JRE?

As you can see on below screenshots, eclipse and Android SDK Manager (and other Java programs) are trying to connect to a IPv4 Internet IP via IPv6 TCP/IP stack while Proxifier (a proxy manager program, nevermind) can not support that.

How I can disable IPv6 in Java?

Make docker use IPv4 for port binding

I have docker host and inside I have one container.

The docker host is binding the port on IPv6 interface only, not on IPv4.

This is the output

tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      -
tcp        0      0 0.0.0.0:55082           0.0.0.0:*               LISTEN      -
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      -
tcp6       0      0 :::80                   :::*                    LISTEN      -
tcp6       0      0 :::22                   :::*                    LISTEN      -
tcp6       0      0 :::40280                :::*                    LISTEN      -
tcp6       0      0 :::5432                 :::*                    LISTEN      -
tcp6       0      0 :::40122                :::*                    LISTEN      -
tcp6       0      0 :::36378                :::*                    LISTEN      -
tcp6       0      0 :::40543                :::*                    LISTEN      -
tcp6       0      0 :::111                  :::*                    LISTEN      -

Now I have 40122 port on host to link with port 22 on container.

I want to SSH into that container but I am not able to as its only bound to IPv6

This is my docker version Docker version 1.5.0, build a8a31ef

docker ps

201bde6c839a        myapp:latest   "supervisord -n"    3 weeks ago         Up 2 hours          0.0.0.0:40122->22/tcp, 0.0.0.0:40280->80/tcp, 0.0.0.0:40543->443/tcp   myapp

I ran using docker run -d -P -p 40122:22

netstat -tlna

tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:3031          0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:6379            0.0.0.0:*               LISTEN
tcp6       0      0 :::22                   :::*                    LISTEN
tcp6       0      0 :::6379                 :::*                    LISTEN

ps aux

root         1  0.0  0.8  52440 16668 ?        Ss   00:53   0:03 /usr/bin/python /usr/bin/supervisord -n
root        49  0.0  0.1  17980  3048 ?        S    01:32   0:00 bash
root        64  0.0  0.1  46632  2712 ?        S    01:32   0:00 su -l vagrant
vagrant     65  0.0  0.1  21308  3760 ?        S    01:32   0:00 -su
root       288  0.0  0.1  17980  3088 ?        S    02:01   0:00 bash
root       304  0.0  0.1  46632  2720 ?        S    02:01   0:00 su -l vagrant
vagrant    305  0.0  0.1  21304  3804 ?        S    02:01   0:00 -su
vagrant    308  0.0  3.7 429616 75840 ?        Sl+  02:01   0:05 python ./manage.py shell_plus
root       654  0.0  0.4  47596  9848 ?        S    03:12   0:01 /usr/local/bin/uwsgi --die-on-term --ini /var/www/conf/uwsgi.ini
root       655  0.0  0.3  90280  7732 ?        S    03:12   0:00 nginx: master process /usr/sbin/nginx
www-data   656  0.0  0.1  90600  3624 ?        S    03:12   0:00 nginx: worker process
www-data   657  0.0  0.1  90600  3624 ?        S    03:12   0:00 nginx: worker process
www-data   658  0.0  0.1  90600  3624 ?        S    03:12   0:00 nginx: worker process
www-data   659  0.0  0.2  90940  4500 ?        S    03:12   0:00 nginx: worker process
root       660  0.0  0.2  61372  5332 ?        S    03:12   0:00 /usr/sbin/sshd -D
root       669  0.0  0.4  37004  8892 ?        Sl   03:12   0:01 redis-server *:6379
root       856  8.0  2.8 388720 57792 ?        Sl   04:07   0:18 /usr/local/bin/uwsgi --die-on-term --ini /var/www/conf/uwsgi.ini
root       857  8.0  2.8 388720 57792 ?        Sl   04:07   0:18 /usr/local/bin/uwsgi --die-on-term --ini /var/www/conf/uwsgi.ini
root       858  8.0  2.8 388720 57792 ?        Sl   04:07   0:18 /usr/local/bin/uwsgi --die-on-term --ini /var/www/conf/uwsgi.ini
root       859  8.0  2.8 388720 57792 ?        Sl   04:07   0:18 /usr/local/bin/uwsgi --die-on-term --ini /var/www/conf/uwsgi.ini
vagrant    889  0.0  0.1  18692  2508 ?        R+   04:11   0:00 ps aux

How to convert an address from IPv4 to IPv6

Is this possible? How can you convert an ipv4 to an ipv6 address?

a few example from here:

0.0.0.0   -> ::
127.0.0.1 -> ::1

I'm searching a solution in Java.

Thanks,

How do you make IPV6 default in Chrome for MAC?

I've been to chrome://net-internals/#dns and enabled IPV6 but there does not seem to be an option to have the browser try the IPV6 address first, it's defaulting to IPV4.

Before enabling IPV6 the default address family was: Default adress family: ADDRESS_FAMILY_IPV4 (IPv6 disabled) After enabling IPV6 it shows as: Default adress family: ADDRESS_FAMILY_UNSPECIFIED

This looked promising for a sec until it grabbed the IPV4 address first. Any help would be appreciated or even confirmation that it isn't possible.

Maximum length of the textual representation of an IPv6 address?

I want to store the data returned by $_SERVER["REMOTE_ADDR"] in PHP into a DB field, pretty simple task, really. The problem is that I can't find any proper information about the maximum length of the textual representation of an IPv6 address, which is what a webserver provides through $_SERVER["REMOTE_ADDR"].

I'm not interested in converting the textual representation into the 128 bits the address is usually encoded in, I just want to know how many characters maximum are needed to store any IPv6 address returned by $_SERVER["REMOTE_ADDR"].

Is there a way for non-root processes to bind to "privileged" ports (<1024) on Linux?

It's very annoying to have this limitation on my development box, when there won't ever be any users other than me.

I'm aware of the standard workarounds, but none of them do exactly what I want:

1. authbind (The version in Debian testing, 1.0, only supports IPv4)
2. Using the iptables REDIRECT target to redirect a low port to a high port (the "nat" table is not yet implemented for ip6tables, the IPv6 version of iptables)
3. sudo (Running as root is what I'm trying to avoid)
4. SELinux (or similar). (This is just my dev box, I don't want to introduce a lot of extra complexity.)

So is there some simple sysctl variable for this, or am I just out of luck?

EDIT: In some cases, you can use capabilities to do this.

what does "dead beef" mean?

What does the word "dead beef" mean? I read it from a interview question. It has something to do with ipv6. I figured it could be a random hex number used for examples, like "The quick brown fox jumps over the lazy dog".

Is my understanding correct? Or it has more significant meaning?