mqtt

MQTT Reason Codes

Single-byte reason codes returned in MQTT 5.0 control packets (CONNACK, PUBACK, PUBREC, PUBREL, PUBCOMP, SUBACK, UNSUBACK, DISCONNECT, and AUTH). Defined in the OASIS MQTT Version 5.0 specification, section 2.4.

43 codes

references docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html

· All codes 43 codes

BadAuthenticationMethod Bad Authentication Method The authentication method specified in the CONNECT packet is not supported or does not match the currently-in-use authentication method. Sent in a CONNACK or DISCONNECT packet.
BadUserNameOrPassword Bad User Name Or Password The server did not accept the User Name or Password supplied by the client. Sent in a CONNACK packet when authentication credentials are malformed or incorrect.
Banned Banned The client has been banned by administrative action. Sent in a CONNACK packet; the client should not attempt to reconnect until it has been explicitly unbanned.
ClientIdentifierNotValid Client Identifier Not Valid The Client Identifier is a valid string but is not permitted by the server. Sent in a CONNACK packet when the server rejects the client's identifier, for example because it is too long or contains disallowed characters.
ConnectionRateExceeded Connection Rate Exceeded The connection rate limit has been exceeded. Sent in a CONNACK or DISCONNECT packet when the client is connecting at a rate greater than permitted by the server.
ContinueAuthentication Continue Authentication Continue the authentication exchange with another step. Sent in an AUTH packet during an extended authentication flow to signal that additional data must be exchanged before authentication can complete.
DisconnectWithWillMessage Disconnect With Will Message The client disconnects but requests that the server publish its Will Message before removing the session. Sent by the client in a DISCONNECT packet to trigger Will Message publication on a deliberate close.
GrantedQoS0 Granted QoS 0 The subscription was accepted and the maximum QoS granted is QoS 0. Sent in a SUBACK packet when the broker accepts the subscription but limits delivery to at-most-once semantics.
GrantedQoS1 Granted QoS 1 The subscription was accepted and the maximum QoS granted is QoS 1. Sent in a SUBACK packet when the broker accepts the subscription with at-least-once delivery semantics.
GrantedQoS2 Granted QoS 2 The subscription was accepted and the maximum QoS granted is QoS 2. Sent in a SUBACK packet when the broker accepts the subscription with exactly-once delivery semantics.
ImplementationSpecificError Implementation Specific Error The operation is valid but the receiver has chosen not to accept it for an implementation-specific reason. Used in CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, and DISCONNECT packets.
KeepAliveTimeout Keep Alive Timeout The connection is being closed because no packet was received within one and a half times the Keep Alive period. Sent by the server in a DISCONNECT packet.
MalformedPacket Malformed Packet The received packet does not conform to the MQTT specification and cannot be parsed. Sent in a CONNACK or DISCONNECT packet; the receiver must close the network connection after sending this code.
MessageRateTooHigh Message Rate Too High The received data rate is too high. Sent in a DISCONNECT packet when the sender is publishing at a rate that exceeds the rate permitted by the receiver's current policy.
NoMatchingSubscribers No Matching Subscribers The message was accepted by the server but there are no current subscribers. Sent in a PUBACK or PUBREC packet to inform the publisher that the message was not delivered to any subscriber.
NormalDisconnection Normal Disconnection The client or server disconnects normally. Sent in a DISCONNECT packet to indicate a clean, intentional close of the connection with no error condition.
NoSubscriptionFound No Subscription Found No matching subscription was found on the server when processing the UNSUBSCRIBE request. Sent in an UNSUBACK packet to indicate the topic filter was not present in the client's subscriptions.
NotAuthorized Not Authorized The client is not authorised to perform the requested operation. Used in CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, and DISCONNECT packets when an authorisation policy denies access.
PacketIdentifierInUse Packet Identifier In Use The specified Packet Identifier is already in use for an outstanding QoS 1 or QoS 2 message. Sent in a PUBACK or SUBACK packet to indicate a protocol flow conflict.
PacketIdentifierNotFound Packet Identifier Not Found The Packet Identifier referenced in a PUBREL or PUBCOMP packet is not known. Sent in a PUBREL or PUBCOMP packet when no matching unreleased or unacknowledged QoS 2 message exists.
PacketTooLarge Packet Too Large The PUBLISH packet exceeded the maximum permissible size. Sent in a CONNACK or DISCONNECT packet when a packet exceeds the Maximum Packet Size declared by the receiver.
PayloadFormatInvalid Payload Format Invalid The payload format does not match the Payload Format Indicator in the PUBLISH packet. Sent in a CONNACK, PUBACK, PUBREC, or DISCONNECT packet when the payload content does not conform to the declared format.
ProtocolError Protocol Error An unexpected or out-of-order packet was received that violates the protocol state machine. Sent in a CONNACK or DISCONNECT packet; the receiver must close the network connection after sending this code.
QoSNotSupported QoS Not Supported The QoS level requested is higher than the Maximum QoS supported by the server. Sent in a CONNACK or DISCONNECT packet when the client publishes or subscribes at a QoS the server does not support.
QuotaExceeded Quota Exceeded An implementation- or deployment-specific limit has been exceeded. Sent in a CONNACK, PUBACK, PUBREC, SUBACK, or DISCONNECT packet when a quota such as message storage or connection count is reached.
ReAuthenticate Re-authenticate The client is initiating a re-authentication attempt. Sent by the client in an AUTH packet on an already-established connection to begin a new authentication exchange.
ReceiveMaximumExceeded Receive Maximum Exceeded The client or server has received more than Receive Maximum publications for which it has not sent a PUBACK or PUBCOMP. Sent in a DISCONNECT packet to report a violation of the flow control limit.
RetainNotSupported Retain Not Supported The server does not support retained messages. Sent in a CONNACK or DISCONNECT packet when the client publishes a RETAIN message to a server that has not announced support for it.
ServerBusy Server Busy The server is busy and cannot process the request. Sent in a CONNACK or DISCONNECT packet; the client should wait before retrying the connection.
ServerMoved Server Moved The client should permanently change the server to which it connects. Sent in a CONNACK or DISCONNECT packet; the server supplies the new address in the Server Reference property and the client must not reconnect to the original server.
ServerShuttingDown Server Shutting Down The server is shutting down. Sent in a DISCONNECT packet by the server to inform the client that the connection is being closed as part of a planned shutdown.
ServerUnavailable Server Unavailable The MQTT server is not available. Sent in a CONNACK packet when the server is temporarily unable to accept the connection, for example during an overload or maintenance window.
SessionTakenOver Session Taken Over Another connection using the same Client Identifier has connected, causing this session to be closed. Sent by the server in a DISCONNECT packet when a new connection with the same client ID is accepted.
SharedSubscriptionsNotSupported Shared Subscriptions Not Supported Shared subscriptions are not supported by this server. Sent in a SUBACK or DISCONNECT packet when the client attempts to create a shared subscription on a server that does not support the feature.
SubscriptionIdentifiersNotSupported Subscription Identifiers Not Supported The server does not support Subscription Identifiers. Sent in a SUBACK or DISCONNECT packet when a client includes a Subscription Identifier in a SUBSCRIBE packet and the server has not announced support.
Success Success The operation completed successfully. Used in CONNACK, PUBACK, PUBREC, PUBREL, PUBCOMP, UNSUBACK, and AUTH packets to indicate the requested operation was accepted and completed without error.
TopicAliasInvalid Topic Alias Invalid The Topic Alias sent by the client is greater than the Topic Alias Maximum the server declared, or a Topic Alias of 0 was used. Sent in a DISCONNECT packet to report the invalid alias.
TopicFilterInvalid Topic Filter Invalid The topic filter provided is correctly formed but is not accepted by the server. Sent in a SUBACK or UNSUBACK packet when the server rejects the topic filter for policy reasons.
TopicNameInvalid Topic Name Invalid The topic name provided is not malformed but is not accepted by the server or client. Used in CONNACK, PUBACK, PUBREC, and DISCONNECT packets when a topic name violates server policy.
UnspecifiedError Unspecified Error The operation failed but the sender does not wish to reveal the reason, or none of the other reason codes apply. Used in CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, and DISCONNECT packets.
UnsupportedProtocolVersion Unsupported Protocol Version The server does not support the version of the MQTT protocol requested by the client. Sent in a CONNACK packet when the client's protocol level field is not recognised by the server.
UseAnotherServer Use Another Server The client should temporarily change the server to which it connects. Sent in a CONNACK or DISCONNECT packet; the server may supply the preferred server address in the Server Reference property.
WildcardSubscriptionsNotSupported Wildcard Subscriptions Not Supported The server does not support wildcard subscriptions. Sent in a SUBACK or DISCONNECT packet when a client attempts to subscribe using a topic filter containing wildcard characters on a server that does not support them.