SSE Protocol

The SSE plugin discovers and subscribes to Server-Sent Events endpoints in your ASP.NET application.

Package: Kuestenlogik.Bowire.Protocol.Sse

Setup

dotnet add package Kuestenlogik.Bowire.Protocol.Sse

Using the Attribute

Mark your SSE endpoints with [SseEndpoint]:

app.MapGet("/events/ticker", [SseEndpoint(Description = "Live price updates", EventType = "price")]
async (HttpContext ctx) =>
{
    ctx.Response.ContentType = "text/event-stream";
    // ... emit SSE events
});

app.MapBowire();

Using Fluent Registration

Register endpoints manually before mapping Bowire:

app.AddBowireSseEndpoint("/events/ticker", "Ticker", "Live price updates", "price,status");
app.MapBowire();

Using Produces Metadata

Endpoints with Produces("text/event-stream") metadata are also discovered automatically.

Discovery

The SSE plugin finds endpoints through three mechanisms:

  1. [SseEndpoint] attribute -- endpoints decorated with the attribute
  2. Produces("text/event-stream") metadata -- endpoints with SSE content type
  3. Manual registration -- endpoints added via AddBowireSseEndpoint()

In embedded mode, the plugin scans EndpointDataSource for matching endpoints.

Streaming

SSE is streaming-only -- there is no request/response pattern. When you select an SSE endpoint in Bowire and click Subscribe, the plugin connects to the endpoint and streams events to the UI.

Each SSE event is parsed according to the standard format:

Field Description
id Event identifier (for reconnection)
event Event type name
data Event payload
retry Reconnection interval in milliseconds

Events are displayed in the response viewer as JSON objects containing all parsed fields.

Limitations

  • Server-to-client only -- SSE is unidirectional. There is no request body or duplex support.
  • No interactive channels -- OpenChannelAsync returns null for SSE endpoints.
  • Embedded mode recommended -- endpoint discovery via attribute scanning requires access to the application's endpoint metadata.

URL Override

You can override the target URL in the request body:

{
  "url": "/events/custom-path"
}

If the URL starts with http, it is used as-is. Otherwise, it is appended to the configured server URL.

See also: Quick Start, Streaming

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