The Internet Namespace

This section describes the details of the protocols and socket naming conventions used in the Internet namespace.

Originally the Internet namespace used only IP version 4 (IPv4). With the growing number of hosts on the Internet, a new protocol with a larger address space was necessary: IP version 6 (IPv6). IPv6 introduces 128-bit addresses (IPv4 has 32-bit addresses) and other features, and will eventually replace IPv4.

To create a socket in the IPv4 Internet namespace, use the symbolic name PF_INET of this namespace as the namespace argument to socket or socketpair. For IPv6 addresses you need the macro PF_INET6. These macros are defined in `sys/socket.h'.

Macro: int PF_INET

This designates the IPv4 Internet namespace and associated family of protocols.

Macro: int PF_INET6

This designates the IPv6 Internet namespace and associated family of protocols.

A socket address for the Internet namespace includes the following components:

• The address of the machine you want to connect to. Internet addresses can be specified in several ways; these are discussed in section Internet Socket Address Formats, section Host Addresses and section Host Names.
• A port number for that machine. See section Internet Ports.

You must ensure that the address and port number are represented in a canonical format called network byte order. See section Byte Order Conversion, for information about this.

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