Broken Java networking in Debian

Playing around with Java I ran into the problem well known as Bug #560044. Seems that the problem appears for Debian GNU/Linux only. The essence of the issue is: when you run any Java application that requires network access (by HTTP or by other protocol; it does not matter) you will (as well as the running application itself) receive the following error. Or a very similar one:

Exception in thread "main" java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

This stack trace says nothing specific about occurred error except that a connection with a remote server cannot be established. The problem is at the bottom of explicitly set in Debian bindv6only kernel parameter. When it turned on (set to "1" in terms of sysctl) it means that network-requesting application will receive IPv6 socket by default not IPv4. To be able to use IPv4 socket an application should open it explicitly. Since some applications rely on the host system's settings it leads that they may fail while network access (details).

The solution is pretty easy: to disable explicit IPv6 binding in your Debian GNU/Linux. This can be done by the command execution:

echo 0 | sudo tee -a /proc/sys/net/ipv6/bindv6only 

This snippet will fix the problem for the current session only. To make the changes in Debian permanent the another one should be performed (proposed by Heikki Henriksen):

sudo sed -i 's/net.ipv6.bindv6only\ =\ 1/net.ipv6.bindv6only\ =\ 0/' /etc/sysctl.d/bindv6only.conf && sudo invoke-rc.d procps restart

After this fix (I believe that it is still a w/a) Java applications can have network access and not raise incomprehensible exceptions anymore.