#### async_connect (1 of 4 overloads)

Asynchronously establishes a socket connection by trying each endpoint in a sequence.

    template<
        typename Protocol,
        typename Executor,
        typename EndpointSequence,
        typename RangeConnectToken = default_completion_token_t<Executor>>
    DEDUCED async_connect(
        basic_socket< Protocol, Executor > & s,
        const EndpointSequence & endpoints,
        RangeConnectToken && token = default_completion_token_t< Executor >(),
        constraint_t< is_endpoint_sequence< EndpointSequence >::value >  = 0,
        constraint_t< !is_connect_condition< RangeConnectToken, decltype(declval< const EndpointSequence & >().begin())>::value >= 0);

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.

###### Parameters

s

  The socket to be connected. If the socket is already open, it will be closed.

endpoints

  A sequence of endpoints.

token

  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, the successfully connected endpoint.
        // Otherwise, a default-constructed endpoint.
        const typename Protocol::endpoint& endpoint
      );

  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 `async_immediate`.

###### Completion Signature

    void(asio::error_code, typename Protocol::endpoint)

###### Example

    tcp::resolver r(my_context);
    tcp::resolver::query q("host", "service");
    tcp::socket s(my_context);

    // ...

    r.async_resolve(q, resolve_handler);

    // ...

    void resolve_handler(
        const asio::error_code& ec,
        tcp::resolver::results_type results)
    {
      if (!ec)
      {
        asio::async_connect(s, results, connect_handler);
      }
    }

    // ...

    void connect_handler(
        const asio::error_code& ec,
        const tcp::endpoint& endpoint)
    {
      // ...
    }

###### Per-Operation Cancellation

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.