Protobuf serializer package

Package: Pulse.Mqtt.Serialization.Protobuf

Use this package when typed MQTT payloads are generated Protocol Buffers messages and deserialization should use explicit parser registration instead of reflection-based discovery.

Install

dotnet add package Pulse.Mqtt.Serialization.Protobuf

Register message parsers

Register every generated message type that the client must deserialize:

using Pulse.Mqtt.Serialization.Protobuf;

var registry = ProtobufMessageRegistry.Create(registry =>
{
    registry.Add(TelemetryReading.Parser);
    registry.Add(StatusRequest.Parser);
    registry.Add(StatusReply.Parser);
});

var serializer = new ProtobufMqttSerializer(registry);

Parser registration is explicit by design. It keeps the package trim/Native AOT friendly and avoids scanning assemblies at runtime.

Configure with dependency injection

builder.Services
    .AddPulseMqttClient("telemetry", configure)
    .UseSerializer(_ => new ProtobufMqttSerializer(registry));

Configure directly

var options = new ResilientMqttClientOptions
{
    Connect = new MqttConnectPacket { ClientId = "telemetry-worker" },
    Serializer = new ProtobufMqttSerializer(registry),
};

Customize metadata

The default metadata is:

Field	Value
ContentType	application/x-protobuf
PayloadFormatIndicator	Unspecified

Use ProtobufMqttSerializerOptions when the application needs a different content type:

var serializer = new ProtobufMqttSerializer(new ProtobufMqttSerializerOptions
{
    Registry = registry,
    ContentType = "application/vnd.example.telemetry+protobuf",
});

Use typed APIs

await client.PublishAsync(
    "telemetry/device-7",
    new TelemetryReading { DeviceId = "device-7", Value = 21.5 },
    MqttQualityOfService.AtLeastOnce,
    cancellationToken: ct);

var template = MqttRouteTemplate.Parse("telemetry/{deviceId}");
await client.SubscribeAsync([template.ToTopicFilter(MqttQualityOfService.AtLeastOnce)], ct);

using var route = client.RegisterRoute<TelemetryReading>(
    template,
    (reading, message, token) => HandleAsync(reading, message.Values["deviceId"], token));

Requirements and limitations

• Values passed to typed publish APIs must implement the generated-message interfaces.
• Deserialization requires a registered parser for the target type.
• Invalid payloads and missing parsers throw MqttException.
• The package does not infer message types from MQTT topics or content types.

Related docs

• Typed messaging
• Native AOT
• Serializer package overview