Endpoint requirements

An endpoint 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 an endpoint class, a denotes a value of type X, s denotes a size in bytes, and u denotes an identifier.

Table 10. Endpoint requirements

expression	type	assertion/note pre/post-conditions
`X::protocol_type`	type meeting protocol requirements
`X u;`
`X();`
`a.protocol();`	`protocol_type`
`a.data();`	a pointer	Returns a pointer suitable for passing as the address argument to POSIX functions such as `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`. The implementation shall perform a `reinterpret_cast` on the pointer to convert it to `sockaddr*`.
`const X& u = a; u.data();`	a pointer	Returns a pointer suitable for passing as the address argument to POSIX functions such as `connect()`, or as the dest_addr argument to POSIX functions such as `sendto()`. The implementation shall perform a `reinterpret_cast` on the pointer to convert it to `const sockaddr*`.
`a.size();`	`size_t`	Returns a value suitable for passing as the address_len argument to POSIX functions such as `connect()`, or as the dest_len argument to POSIX functions such as `sendto()`, after appropriate integer conversion has been performed.
`a.resize(s);`		post: `a.size() == s` Passed the value contained in the address_len argument to POSIX functions such as `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`, after successful completion of the function. Permitted to throw an exception if the protocol associated with the endpoint object `a` does not support the specified size.
`a.capacity();`	`size_t`	Returns a value suitable for passing as the address_len argument to POSIX functions such as `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`, after appropriate integer conversion has been performed.