[section:Error_handling Error handling]

The table below provides a reference of all __ERROR_CODE__ instances that asynchronous operations
may complete with, along with the reasons for their occurrence.

[table:error_codes Error codes
	[[Error code] [Cause]]
	[[`boost::system::errc::errc_t::success`] [The operation completed successfully.]]
	[[`boost::asio::error::opreation_aborted`] [
		The operation has been cancelled. 
		The cancellation of the operation can be triggered by invoking either [refmem mqtt_client cancel]
		or [refmem mqtt_client async_disconnect]. Furthermore, if a cancellation slot has been associated
		with the __CompletionToken__ provided and the corresponding cancellation signal is emitted,
		the operation will also finish with this error code (see __ASIO_PER_OP_CANCELLATION__).
	]]
	[[`boost::asio::no_recovery`] [
		An non-recoverable error occurred during the attempt by the [reflink2 mqtt_client `mqtt_client`]
		to establish a connection with the Server. The cause of this error may be attributed to the connection 
		related parameters used during the initialization of the [reflink2 mqtt_client `mqtt_client`].
	]]
	[[`async_mqtt5::client::error::malformed_packet`][
		The Client has attempted to send a packet that does not conform to the specification.
		This issue can arise from improperly formed UTF-8 encoded strings.
		Additionally, this error can be caused by providing out-of-range values.
	]]
	[[`async_mqtt5::client::error::packet_too_large`][
		The Client has attempted to send a packet larger than the Maximum Packet Size the Server
		is willing to process.
	]]
	[[`async_mqtt5::client::error::session_expired`][
		The Client has established a successful connection with a Server, but either the session does not exist or has expired.
		In cases where the Client had previously set up subscriptions to Topics, these subscriptions are also expired.
		Therefore, the Client should re-subscribe.
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_receive] calls.
	]]
	[[`async_mqtt5::client::error::pid_overrun`] [
		This error code signifies that the Client was unable to allocate a Packet Identifier for
		the current operation due to the exhaustion of the available identifiers.
		This occurs when there are 65535 outgoing Packets awaiting their responses.
	]]
	[[`async_mqtt5::client::error::invalid_topic`] [
		The Client has attempted to perform an action (publish, subscribe or unsubscribe) on an invalid Topic.
		See __TOPIC_SEMANTIC_AND_USAGE__ for information on properly formed Topics.
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_publish], 
		[refmem mqtt_client async_subscribe], and [refmem mqtt_client async_unsubscribe] calls.
		In the case of [refmem mqtt_client async_subscribe] and [refmem mqtt_client async_unsubscribe], this error code 
		occurs if at least one Topic provided is malformed.
	]]
	[[`async_mqtt5::client::error::qos_not_supported`] [
		The Client has attempted to publish an Application Message with __QOS__ higher
		than the Maximum __QOS__ specified by the Server.
		The Server does not support this __QOS__ (see __MAXIMUM_QOS__).
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_publish] calls.
	]]
	[[`async_mqtt5::client::error::retain_not_available`] [
		The Client has attempted to publish an Application Message with the __RETAIN__ flag set to 1.
		However, the Server does not support retained messages (see __RETAIN_AVAILABLE__).
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_publish] calls.
	]]
	[[`async_mqtt5::client::error::topic_alias_maximum`] [
		The Client has attempted to publish an Application Message with the Topic Alias 
		exceeding the Server's supported Topic Alias Maximum. Additionally, this error code
		will arise in instances when the Server does NOT support Topic Aliases, and the 
		Client has attempted to use them. See __TOPIC_ALIAS_MAX__.
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_publish] calls.
	]]
	[[`async_mqtt5::client::error::wildcard_subscription_not_available`] [
		The Client has attempted to subscribe to multiple Topics using Wildcard Character (`+` and/or `#`).
		However, the Server does not support Wildcard Subscriptions.
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_subscribe] calls.
	]]
	[[`async_mqtt5::client::error::subscription_identifier_not_available`] [
		The Client has attempted to associate a subscription with a Subscription Identifier.
		However, the Server either does not support Subscription Identifiers or the Subscription Identifier provided
		is out of range (the Subscription Identifier can have a value of 1 to 268,435,455).
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_subscribe] calls.
	]]
	[[`async_mqtt5::client::error::shared_subscription_not_available`] [
		The Client has attempted to establish a Shared Subscription.
		However, the Server does not support Shared Subscriptions.
		This error code is exclusive to completion handlers associated with [refmem mqtt_client async_subscribe] calls.
	]]
]

[endsect]