Protocol requirements

A protocol must meet the requirements of CopyConstructible types (C++ Std, 20.1.3), and the requirements of Assignable types (C++ Std, 23.1).

In the table below, X denotes a protocol class, and a denotes a value of X.

Table 19. Protocol requirements

expression	return type	assertion/note pre/post-conditions
`X::endpoint`	type meeting endpoint requirements
`a.family()`	`int`	Returns a value suitable for passing as the domain argument to POSIX `socket()` (or equivalent).
`a.type()`	`int`	Returns a value suitable for passing as the type argument to POSIX `socket()` (or equivalent).
`a.protocol()`	`int`	Returns a value suitable for passing as the protocol argument to POSIX `socket()` (or equivalent).

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