// Copyright 2020-2026 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Adapted from server/mqtt.go in the NATS server Go source.
namespace ZB.MOM.NatsNet.Server.Mqtt;
// References to "spec" here are from https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.pdf
///
/// MQTT control packet type byte values.
/// Mirrors the mqttPacket* constants in server/mqtt.go.
///
internal static class MqttPacket
{
public const byte Connect = 0x10;
public const byte ConnectAck = 0x20;
public const byte Pub = 0x30;
public const byte PubAck = 0x40;
public const byte PubRec = 0x50;
public const byte PubRel = 0x60;
public const byte PubComp = 0x70;
public const byte Sub = 0x80;
public const byte SubAck = 0x90;
public const byte Unsub = 0xA0;
public const byte UnsubAck = 0xB0;
public const byte Ping = 0xC0;
public const byte PingResp = 0xD0;
public const byte Disconnect = 0xE0;
public const byte Mask = 0xF0;
public const byte FlagMask = 0x0F;
}
///
/// MQTT CONNECT packet flag byte values.
/// Mirrors the mqttConnFlag* constants in server/mqtt.go.
///
internal static class MqttConnectFlag
{
public const byte Reserved = 0x01;
public const byte CleanSession = 0x02;
public const byte WillFlag = 0x04;
public const byte WillQoS = 0x18;
public const byte WillRetain = 0x20;
public const byte PasswordFlag = 0x40;
public const byte UsernameFlag = 0x80;
}
///
/// MQTT PUBLISH packet flag byte values.
/// Mirrors the mqttPubFlag* and mqttPubQoS* constants in server/mqtt.go.
///
internal static class MqttPubFlag
{
public const byte Retain = 0x01;
public const byte QoS = 0x06;
public const byte Dup = 0x08;
public const byte QoS1 = 0x1 << 1;
public const byte QoS2 = 0x2 << 1;
}
///
/// MQTT CONNACK return codes.
/// Mirrors the mqttConnAckRC* constants in server/mqtt.go.
///
internal static class MqttConnAckRc
{
public const byte Accepted = 0x00;
public const byte UnacceptableProtocol = 0x01;
public const byte IdentifierRejected = 0x02;
public const byte ServerUnavailable = 0x03;
public const byte BadUserOrPassword = 0x04;
public const byte NotAuthorized = 0x05;
public const byte QoS2WillRejected = 0x10;
}
///
/// Miscellaneous MQTT protocol constants.
/// Mirrors the remaining scalar constants in server/mqtt.go.
///
internal static class MqttConst
{
/// Maximum control packet payload size (0xFFFFFFF).
public const int MaxPayloadSize = 0xFFFFFFF;
/// MQTT topic level separator character ('/').
public const char TopicLevelSep = '/';
/// Single-level wildcard character ('+').
public const char SingleLevelWildcard = '+';
/// Multi-level wildcard character ('#').
public const char MultiLevelWildcard = '#';
/// Reserved topic prefix character ('$').
public const char ReservedPrefix = '$';
/// MQTT protocol level byte (v3.1.1 = 0x04).
public const byte ProtoLevel = 0x04;
/// SUBACK failure return code (0x80).
public const byte SubAckFailure = 0x80;
/// Fixed flags byte in SUBSCRIBE packets (0x02).
public const byte SubscribeFlags = 0x02;
/// Fixed flags byte in UNSUBSCRIBE packets (0x02).
public const byte UnsubscribeFlags = 0x02;
///
/// Suffix appended to the SID of subscriptions created for MQTT '#' wildcard
/// at the upper level. Mirrors mqttMultiLevelSidSuffix.
///
public const string MultiLevelSidSuffix = " fwc";
/// Initial byte allocation for publish headers (overestimate).
public const int InitialPubHeader = 16;
/// Default maximum number of pending QoS-1 acks per session.
public const int DefaultMaxAckPending = 1024;
/// Absolute upper limit on cumulative MaxAckPending across all session subscriptions.
public const int MaxAckTotalLimit = 0xFFFF;
/// WebSocket path for MQTT connections.
public const string WsPath = "/mqtt";
/// Marker character for deleted retained messages (used in flag field).
public const char RetainedFlagDelMarker = '-';
}
///
/// MQTT-internal NATS subject / stream / consumer name constants.
/// Mirrors the string constants in server/mqtt.go that define JetStream stream names,
/// subject prefixes, and JSA reply tokens.
///
internal static class MqttTopics
{
// -------------------------------------------------------------------------
// Top-level MQTT subject prefix
// -------------------------------------------------------------------------
/// Prefix used for all internal MQTT subjects.
public const string Prefix = "$MQTT.";
///
/// Prefix for NATS subscriptions used as JS consumer delivery subjects.
/// MQTT clients must not subscribe to subjects starting with this prefix.
///
public const string SubPrefix = Prefix + "sub.";
// -------------------------------------------------------------------------
// JetStream stream names
// -------------------------------------------------------------------------
/// Stream name for MQTT QoS >0 messages on a given account.
public const string MsgsStreamName = "$MQTT_msgs";
/// Subject prefix for messages in the MQTT messages stream.
public const string MsgsStreamSubjectPrefix = Prefix + "msgs.";
/// Stream name for MQTT retained messages.
public const string RetainedMsgsStreamName = "$MQTT_rmsgs";
/// Subject prefix for messages in the retained messages stream.
public const string RetainedMsgsStreamSubject = Prefix + "rmsgs.";
/// Stream name for MQTT session state.
public const string SessStreamName = "$MQTT_sess";
/// Subject prefix for session state messages.
public const string SessStreamSubjectPrefix = Prefix + "sess.";
/// Name prefix used when creating per-account session streams.
public const string SessionsStreamNamePrefix = "$MQTT_sess_";
/// Stream name for incoming QoS-2 messages.
public const string QoS2IncomingMsgsStreamName = "$MQTT_qos2in";
/// Subject prefix for incoming QoS-2 messages.
public const string QoS2IncomingMsgsStreamSubjectPrefix = Prefix + "qos2.in.";
/// Stream name for outgoing MQTT QoS messages (PUBREL).
public const string OutStreamName = "$MQTT_out";
/// Subject prefix for outgoing MQTT messages.
public const string OutSubjectPrefix = Prefix + "out.";
/// Subject prefix for PUBREL messages.
public const string PubRelSubjectPrefix = Prefix + "out.pubrel.";
/// Subject prefix for PUBREL delivery subjects.
public const string PubRelDeliverySubjectPrefix = Prefix + "deliver.pubrel.";
/// Durable consumer name prefix for PUBREL.
public const string PubRelConsumerDurablePrefix = "$MQTT_PUBREL_";
// -------------------------------------------------------------------------
// JSA reply subject prefix and token constants
// -------------------------------------------------------------------------
/// Prefix of the reply subject for JS API requests.
public const string JsaRepliesPrefix = Prefix + "JSA.";
// Token position indices within a JSA reply subject.
public const int JsaIdTokenPos = 3;
public const int JsaTokenPos = 4;
public const int JsaClientIdPos = 5;
// JSA operation token values.
public const string JsaStreamCreate = "SC";
public const string JsaStreamUpdate = "SU";
public const string JsaStreamLookup = "SL";
public const string JsaStreamDel = "SD";
public const string JsaConsumerCreate = "CC";
public const string JsaConsumerLookup = "CL";
public const string JsaConsumerDel = "CD";
public const string JsaMsgStore = "MS";
public const string JsaMsgLoad = "ML";
public const string JsaMsgDelete = "MD";
public const string JsaSessPersist = "SP";
public const string JsaRetainedMsgDel = "RD";
public const string JsaStreamNames = "SN";
// -------------------------------------------------------------------------
// NATS header names injected into re-encoded PUBLISH messages
// -------------------------------------------------------------------------
/// Header that indicates the message originated from MQTT and stores published QoS.
public const string NatsHeader = "Nmqtt-Pub";
/// Header storing the original MQTT topic for retained messages.
public const string NatsRetainedMessageTopic = "Nmqtt-RTopic";
/// Header storing the origin of a retained message.
public const string NatsRetainedMessageOrigin = "Nmqtt-ROrigin";
/// Header storing the flags of a retained message.
public const string NatsRetainedMessageFlags = "Nmqtt-RFlags";
/// Header storing the source of a retained message.
public const string NatsRetainedMessageSource = "Nmqtt-RSource";
/// Header indicating a PUBREL message and storing the packet identifier.
public const string NatsPubRelHeader = "Nmqtt-PubRel";
/// Header storing the original MQTT subject in re-encoded PUBLISH messages.
public const string NatsHeaderSubject = "Nmqtt-Subject";
/// Header storing the subject mapping in re-encoded PUBLISH messages.
public const string NatsHeaderMapped = "Nmqtt-Mapped";
// -------------------------------------------------------------------------
// Sparkplug B constants
// -------------------------------------------------------------------------
public const string SparkbNBirth = "NBIRTH";
public const string SparkbDBirth = "DBIRTH";
public const string SparkbNDeath = "NDEATH";
public const string SparkbDDeath = "DDEATH";
}