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Send an UNSUBSCRIBE
packet to Broker
to unsubscribe from one Topic.
template<
typename CompletionToken = typename asio::default_completion_token<boost::mqtt5::mqtt_client::executor_type
>::type>
decltype(auto)
async_unsubscribe(
const std::string& topic,
const unsubscribe_props& props,
CompletionToken&& token = {});
The Client may still receive residual Application Messages through the
mqtt_client::async_receive
function from
Topics the Client just unsubscribed to.
Name |
Description |
---|---|
|
Topic to unsubscribe from. |
|
An instance of |
|
Completion token that will be used to produce a completion
handler. The handler will be invoked when the operation completes.
On immediate completion, invocation of the handler will be
performed in a manner equivalent to using |
The handler signature for this operation:
void (, // Result of operation. std::vector<
boost::mqtt5::error_code
>, // Vector of Reason Codes containing // the result of unsubscribe operation // for the Topic in the UNSUBSCRIBE packet.
boost::mqtt5::reason_code
boost::mqtt5::unsuback_props
, // Properties received in the UNSUBACK packet. )
The asynchronous operation will complete when one of the following conditions is true:
UNSUBSCRIBE
packet and
has received an UNSUBACK
response from
the Broker.
boost::mqtt5::error_code
in
the handler.
The list of all possible error codes that this operation can finish with:
boost::system::errc::errc_t::success
boost::asio::error::no_recovery
boost::asio::error::operation_aborted
boost::mqtt5::client::error::malformed_packet
boost::mqtt5::client::error::packet_too_large
boost::mqtt5::client::error::pid_overrun
boost::mqtt5::client::error::invalid_topic
Refer to the section on Error handling
to find the underlying causes for each error code.
This asynchronous operation supports cancellation for the following
boost::asio::cancellation_type
values:
cancellation_type::terminal
- invokes mqtt_client::cancel
cancellation_type::partial
& cancellation_type::total
- prevents potential resending of the UNSUBSCRIBE
packet