Proposed resolution:

This resolution is relative to N4656.

1. Edit [socket.acceptor], class template basic_socket_acceptor synopsis, as indicated:

   template<class AcceptableProtocol> 
   class basic_socket_acceptor {
   public:
     […]
     bool is_open() const noexcept;
     […]
   };
   

2. Edit [socket.acceptor.ops] as indicated:

   bool is_open() const noexcept;
   

   -10- Returns: A bool indicating whether this acceptor was opened by a previous call to open or assign.

[ 2018-3-17 Adopted in Jacksonville ]

[ 2017-11-01 Moved to Tentatively Ready after 7 positive votes for P0 on c++std-lib. ]

Addresses: networking.ts

basic_socket::is_open() is noexcept, but the corresponding function on basic_socket_acceptor is not. This is a simple observer with a wide contract and cannot fail.