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Asynchronously establishes a socket connection by trying each endpoint in a sequence.
template< typename Protocol, typename Executor, typename Iterator, typename IteratorConnectToken = default_completion_token_t<Executor>> DEDUCED async_connect( basic_socket< Protocol, Executor > & s, Iterator begin, Iterator end, IteratorConnectToken && token = default_completion_token_t< Executor >());
          This function attempts to connect a socket to one of a sequence of endpoints.
          It does this by repeated calls to the socket's async_connect
          member function, once for each endpoint in the sequence, until a connection
          is successfully established. It is an initiating function for an asynchronous operation,
          and always returns immediately.
        
The socket to be connected. If the socket is already open, it will be closed.
An iterator pointing to the start of a sequence of endpoints.
An iterator pointing to the end of a sequence of endpoints.
                The completion
                token that will be used to produce a completion handler, which
                will be called when the connect completes. Potential completion tokens
                include use_future,
                use_awaitable,
                yield_context,
                or a function object with the correct completion signature. The function
                signature of the completion handler must be:
              
void handler( // Result of operation. if the sequence is empty, set to // asio::error::not_found. Otherwise, contains the // error from the last connection attempt. const asio::error_code& error, // On success, an iterator denoting the successfully // connected endpoint. Otherwise, the end iterator. Iterator iterator );
                Regardless of whether the asynchronous operation completes immediately
                or not, the completion handler will not be invoked from within this
                function. On immediate completion, invocation of the handler will
                be performed in a manner equivalent to using post.
              
void(asio::error_code, Iterator)
std::vector<tcp::endpoint> endpoints = ...; tcp::socket s(my_context); asio::async_connect(s, endpoints.begin(), endpoints.end(), connect_handler); // ... void connect_handler( const asio::error_code& ec, std::vector<tcp::endpoint>::iterator i) { // ... }
          This asynchronous operation supports cancellation for the following cancellation_type
          values:
        
cancellation_type::terminal
            cancellation_type::partial
            
          if they are also supported by the socket's async_connect
          operation.