Asynchronously establishes a socket connection by trying each endpoint in a sequence.
template< typename Protocol, typename EndpointSequence, typename RangeConnectHandler> DEDUCED async_connect( basic_socket< Protocol > & s, const EndpointSequence & endpoints, RangeConnectHandler && handler, typename enable_if< 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.
The socket to be connected. If the socket is already open, it will be closed.
A sequence of endpoints.
The handler to be called when the connect operation completes. Copies will be made of the handler as required. The function signature of the 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 handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent
to using asio::io_context::post()
.
tcp::resolver r(io_context); tcp::resolver::query q("host", "service"); tcp::socket s(io_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) { // ... }