Client-to-Server Streaming

Clients can stream data to the server using StreamItemToServer and StreamCompleteToServer hub methods. This enables scenarios like uploading large files, sending telemetry, or live data feeds.

How it works

The client sends stream items one at a time using the StreamItemToServer hub method, identified by a stream GUID. When the stream is complete, the client sends StreamCompleteToServer.

Server-side handling

The ServerStreamManager correlates stream items by their GUID and delivers them to the requesting ServerMethods class:

public class UploadMethods : ServerMethods<AppHub>
{
    private readonly ServerStreamManager _streams;

    public UploadMethods(ServerStreamManager streams) => _streams = streams;

    public async Task ProcessStream(Guid streamId, CancellationToken ct)
    {
        await foreach (var item in _streams.ReadStream<MyItemType>(streamId, ct))
        {
            // Process each streamed item
            await ProcessItem(item);
        }
    }
}

Error handling

The client can signal an error by passing an error message to StreamCompleteToServer:

// TypeScript
connection.asSignalRHubConnection().send('StreamCompleteToServer', streamId, 'Upload cancelled');

// .NET
connection.AsSignalRHubConnection().SendAsync("StreamCompleteToServer", streamId, "Upload cancelled");

Next steps

• Server-to-Client Streaming — stream from server to client
• Wire Protocol — stream protocol details