In this chapter, we looked briefly at how internet traffic is routed. We learned that there are two Internet Protocol versions, IPv4 and IPv6. IPv4 has a limited number of addresses, and these addresses are running out. One of IPv6's main advantages is that it has enough address space for every system to have its own unique publicly-routable address. The limited address space of IPv4 is largely mitigated by network address translation performed by routers. We also looked at how to detect your local IP address using both utilities and APIs provided by the operating system.
We saw that the APIs provided for listing local IP addresses differ quite a bit between Windows and Unix-based operating systems. In future chapters, we will see that most other networking functions are similar between operating systems, and we can write one portable program that works between operating systems.
It's OK if you didn't pick up all of the details in this chapter. Most of this information is a helpful background, but it's not essential to most network application programming. Details such as network address translation are handled by the network, and these details will not usually need to be explicitly addressed by your programs.
In the next chapter, we will reinforce the ideas covered here by introducing socket-programming APIs.
