WebSockets

ZIO Laminar Tapir also provides support for WebSocket endpoints defined using Tapir. This allows you to create real-time, bidirectional communication channels between the client and server.

Defining WebSocket Endpoints

You can define a WebSocket endpoint using Tapir's webSocketBody directive. For example:

val echo: PublicEndpoint[
    Unit,
    Error,
    ZioStreams.Pipe[WebSocketFrame, WebSocketFrame],
    ZioStreams & WebSockets
  ] =
    endpoint.get
      .out(
        webSocketBody[
          WebSocketFrame,
          CodecFormat.TextPlain,
          WebSocketFrame,
          CodecFormat.TextPlain
        ](
          ZioStreams
        )
      )
      .errorOut(jsonBody[Error])
      .description("WebSocket echo endpoint")

This defines a WebSocket endpoint that echoes back any text frames it receives.

Then, in the same way as for regular endpoints, you can build a ZIO effect from the endpoint and handle the WebSocket communication. But as WebSockets are bidirectional, this time calling the endpoint will return a ZIO effect that produces a Pipe for handling incoming and outgoing messages.

ws <- WebsocketEndpoint.echo(())

You can then use this Pipe to send and receive messages over the WebSocket connection.

Handling WebSocket Communication

To handle WebSocket communication, you can create a Pipe that processes incoming messages and produces outgoing messages. For example, to create an echo server that sends back any message it receives:

 _ <- ws(
          ZStream
            .fromHubWithShutdown(hub)
                 .tap(msg => result.zEmit(s"Sending: $msg"))
      )
       .runForeach {
        case Text(payload, _, _) =>
          result.zEmit(s"Received: $payload")
        case _ => ZIO.unit
      }
    

ws is a function that takes a ZStream of outgoing messages and returns another ZStream of incoming messages. In this example, we create a ZStream from a Hub to send outgoing messages and process incoming messages by logging them.

This setup allows you to create real-time applications using WebSockets with ZIO Laminar Tapir, leveraging the power of ZIO streams for handling bidirectional communication.

See the Full Example