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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)
{
// ...
}