Erle Robotics Python Networking Gitbook Free

IPv6

And having explained all of that, it turns out that this book actually does need to introduce one additional address family, beyond the AF_INET we have used so far: the address family for IPv6, named AF_INET6, which is the way forward into a future where the world does not, in fact, run out of IP addresses.

In Python you can test directly for whether the underlying platform supports IPv6 by checking the has_ipv6 Boolean attribute inside the socket module:

>>> import socket
>>> socket.has_ipv6
True

But note that this does not tell you whether an actual IPv6 interface is up and configured and can currently be used to send packets anywhere; it is purely an assertion about whether IPv6 support has been compiled into the operating system, not about whether it is in use.

The differences that IPv6 will make for your Python code might sound quite daunting, if listed one right after the other:

• Your sockets have to be prepared to have the family AF_INET6 if you are called upon to operate on an IPv6 network.

• No longer do socket names consist of just two pieces, an address and a port number; instead, they can also involve additional coordinates that provide “flow” information and a “scope” identifier.

• The pretty IPv4 octets like 18.9.22.69 that you might already be reading from configuration files or from your command-line arguments will now sometimes be replaced by IPv6 host addresses instead, which you might not even have good regular expressions for yet. They have lots of colons, they can involve hexadecimal numbers, and in general they look quite ugly.