# FetchZioBackend and websockets

**URL:** https://softwaremill.community/t/fetchziobackend-and-websockets/56
**Category:** sttp client
**Created:** [December 30, 2022, 10:02am UTC](https://softwaremill.community/t/fetchziobackend-and-websockets/56 "2022-12-30T10:02:07Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![dacr](https://dub1.discourse-cdn.com/flex005/user_avatar/softwaremill.community/dacr/32/51_2.png) [@dacr](https://softwaremill.community/u/dacr)
#### Post date: [December 30, 2022, 10:02am UTC](https://softwaremill.community/t/fetchziobackend-and-websockets/56/1 "2022-12-30T10:02:07Z")

</div>

Hello, I’m probably doing something wrong while trying to use sttp (3.8.5) from scala.js (1.12.0) with websockets using FetchZioBackend, in the two situations I’ve tested, I got each time the following error message : `sttp.client3.ws.GotAWebSocketException: Got a web socket, but expected normal content`, although the web socket endpoint is working fine.

I’ve checked again the documentation, and it is said that FetchZioBackend supports websockets, so I wonder, do I have to add some configuration in order to enable websockets ?

The scala.js code looks like :

```plaintext
  val backend = FetchZioBackend()

  def processWebsocket(ws: WebSocket[Task]):Task[Unit] = {
    val receiveOne = ws.receiveText().flatMap(res => Console.printLine(s"received $res"))
    receiveOne.forever
  }

  def byHandWebsocketCall() = {
    val request =
      basicRequest
        .get(uri"ws://127.0.0.1:3000/ws/system/events")
        .response(asWebSocket(processWebsocket))

    val response =
      request
        .send(backend)

    Unsafe.unsafe { implicit u =>
      runtime.unsafe.fork {
         response
           .tap(result => Console.printLine(result.toString))
           .tapError(err => Console.printLine(s"--------> $err"))
      }
    }
  }

```

If I test the same websocket endpoint using scala/JVM I didn’t have any issue, consider this scala-cli code which uses HttpClientZioBackend :

```plaintext
//> using scala "3.2.1"
//> using lib "dev.zio::zio:2.0.5"
//> using lib "com.softwaremill.sttp.client3::zio:3.8.5"

import zio.*
import sttp.client3.*, sttp.client3.basicRequest.*, sttp.ws.*

object WebSocketCat extends ZIOAppDefault {
  def processWebsocket(ws: WebSocket[Task]): Task[Unit] = {
    val receiveOne = ws.receiveText().flatMap(res => Console.printLine(s"received $res"))
    val sendOne = Console.readLine.flatMap(line => ws.sendText(s"""{"message":"$line"}"""))
    receiveOne.forever.race(sendOne.forever)
  }

  def run =
    for {
      backend <- sttp.client3.httpclient.zio.HttpClientZioBackend()
      response <- basicRequest
                    .get(uri"ws://127.0.0.1:3000/ws/system/events")
                    .response(asWebSocket(processWebsocket))
                    .send(backend)
    } yield response
}

WebSocketCat.main(Array.empty)

```

I first thought it was a tapir issue, as my first attemps was tapir based (with sttp of course behind the scene), I’ve opened this ticket ([websocket client endpoint GotAWebSocketException exception with http4s and ZIO · Issue #2584 · softwaremill/tapir · GitHub](https://github.com/softwaremill/tapir/issues/2584)), but after taking a look to this conference : [Functional WebSockets - Adam Warski - YouTube](https://www.youtube.com/watch?v=rR7CK5xDn40&ab_channel=ScalaCon) I decided to make a new attempt using a more direct approach, and I got exactly the same issue.

---

<div class="post-metadata">

### Author: ![adamw](https://dub1.discourse-cdn.com/flex005/user_avatar/softwaremill.community/adamw/32/28_2.png) [@adamw](https://softwaremill.community/u/adamw)
#### Post date: [January 3, 2023, 2:55pm UTC](https://softwaremill.community/t/fetchziobackend-and-websockets/56/2 "2023-01-03T14:55:31Z")

</div>

Let’s move this over to this [sttp issue](https://github.com/softwaremill/sttp/issues/1682) to centralise the discussion 🙂