Asynchronously establishes a socket connection by trying each endpoint in a sequence.
template< typename Protocol, typename Executor, typename EndpointSequence, typename RangeConnectToken = DEFAULT> DEDUCED async_connect( basic_socket< Protocol, Executor > & s, const EndpointSequence & endpoints, RangeConnectToken && token = DEFAULT, typename constraint< is_endpoint_sequence< EndpointSequence >::value >::type = 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.
The socket to be connected. If the socket is already open, it will be closed.
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, 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 post
.
void(asio::error_code, typename Protocol::endpoint)
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) { // ... }
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.