Websocket Routes Only Work on FastAPI, not APIRouter

[iwoloschin]

Describe the bug
Websocket routes appear to only work on the main FastAPI object, not on APIRouter objects. When the same function is copied from a FastAPI object to an APIRouter object instead of working properly it just throws a 403.

To Reproduce
Steps to reproduce the behavior:

1. The following works as expected:

from fastapi import FastAPI
app = FastAPI()

@app.websocket_route("/hello")
async def hello(websocket):
    await websocket.accept()
    await websocket.send_text("Hello!")
    response = await websocket.receive_text()
    print(response)
    await websocket.close()
    print("Closed")

2. Moving hello to an APIRouter fails:

# main.py
from fastapi import FastAPI
import other
app = FastAPI()
app.include_router(other.router)

# other.py
from fastapi import APIRouter
router = APIRouter()

@router.websocket_route("/routerhello")
async def hello(websocket):
    await websocket.accept()
    await websocket.send_text("Router Hello!")
    response = await websocket.receive_text()
    print(response)
    await websocket.close()
    print("Router Closed")

Expected behavior
I expect a websocket route to work on both a FastAPI and APIRouter object.

Screenshots
Not applicable.

Environment:

• OS: macOS 10.14.3

• FastAPI Version: 0.9.0

• Python version, get it with: 3.7.2

Additional context
Testing websocket client side with websocat.

[tiangolo]

Thanks for the report!

It was fixed by @euri10 in PR #100.

It is available in FastAPI verson 0.10.0. 🎉 🚀

[iwoloschin]

Just tested it out! I'm impressed at how quickly that was fixed, thanks!

[tiangolo]

Awesome! Kudos to @euri10 for his work 😀🍰🌮

Thanks @iwoloschin for reporting back and closing the issue.

[Kludex]

@brunopcarv This is a 2 years old issue... You'll have better chances of getting help if you create a new one. 😗

[Udayaprasad]

@euri10 @tiangolo

Looks like this bug again comes in the 0.67.0 - latest version. Could you please check once?

APIRouter prefix is not getting utilized in @router.websocket('/') endpoint definition. I am getting 403 error.

router = APIRouter(
    prefix="/substructures",
    tags=["Substructures"],
    responses={404: {"description": "Not found"}},
)

@router.websocket('/')
async def websocket_execute(websocket: WebSocket):
    ....

[ghost]

@euri10 @tiangolo

Looks like this bug again comes in the 0.67.0 - latest version. Could you please check once?

APIRouter prefix is not getting utilized in @router.websocket('/') endpoint definition. I am getting 403 error.

router = APIRouter(
    prefix="/substructures",
    tags=["Substructures"],
    responses={404: {"description": "Not found"}},
)

@router.websocket('/')
async def websocket_execute(websocket: WebSocket):
    ....

the same bug is present in version 0.65.1

[usotsuki777]

@euri10 @tiangolo
Looks like this bug again comes in the 0.67.0 - latest version. Could you please check once?
APIRouter prefix is not getting utilized in @router.websocket('/') endpoint definition. I am getting 403 error.

router = APIRouter(
    prefix="/substructures",
    tags=["Substructures"],
    responses={404: {"description": "Not found"}},
)

@router.websocket('/')
async def websocket_execute(websocket: WebSocket):
    ....

the same bug is present in version 0.65.1

I have same issue with API-Router. return 403 response .

• python : 3.9.5
• fast-api : 0.68.1
• os : ubuntu 20.04

---

UPDATE

I was trying with another way. The Result is, it's working in app.mount() method.
A codes are below.

websocket method : ws.py

# ws.py
from fastapi import FastAPI, WebSocket
from fastapi.middleware.cors import CORSMiddleware

ws = FastAPI()

# Your CORS
ws.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# websocket
@ws.websocket("/")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()

    while True:
        data = await websocket.receive_text()
        await websocket.send_text(f"Message text was: {data}")

main file : main.py

import uvicorn
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

# import  ws.py for 'mounted'
from ws import ws

app = FastAPI()

# Your CORS
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# mount ws.py
app.mount("/ws", ws)

# ... your routes OR something ...


if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

I feel like, it's better way to use in app.mount() instead of APIRouter() in current time.

[farlabjavier]

same error in 0.68.1

[nanacnote]

I have the same issue at the moment if i set the prefix param in APIRoute() and try to connect to said route it raises 403 however if i drop the prefix it connects successfully. Thank you.

server

router = APIRouter(prefix="/service", tags=["service"])

@router.websocket("/data/market")
async def market_data(websocket: WebSocket):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(f"Message text was: {data}")

client

const s = new WebSocket("ws://localhost:5000/service/data/market")  //---> not working 
const s = new WebSocket("ws://localhost:5000/data/market")  //--->  working

[mntolia]

I am also facing the exact same issue. I am getting a 403 error for websockets under routers with prefix. It works without the prefix.

[obrua]

same error in 0.70.0

[XCanG]

Still getting this issue on fastapi==0.73.0.

[xiki808]

Same issue as mentioned @nanacnote

[lokaimoma]

Same issue in fastapi==0.73.0

[fujiawei-dev]

Same issue in fastapi==0.74.0

[mosynaq]

Applying (read monkey patching) this saved my day. Waiting for @tiangolo to accept this PR.

[dnilosek]

Running into same issue, can that fix be included soon?

[sandiandian]

Same issue in fastapi==0.75.1

[tiangolo]

Hey all! Some of you might have been experiencing a similar issue related to APIRouters with prefix. That was reported here: #2639

It was fixed by @Kludex here: #2640

And that fix will be available in FastAPI version 0.75.2, released in a couple of hours. 🚀

[philipokiokio]

Hi everyone thanks for the help and for fixing this issue.

Truthfully the WebSocket fix works in development (Uvicorn server), however, in production (Ubuntu environment) the websocket did not connect to the APIRouter specified.

For the WebSocket to connect I used the /ws (test.com/ws) rather than the route I specified (test.com/test/flow/ws).
I just wanted to bring that to everyone's notice.

[philipokiokio]

Another thing I noticed is that the WebSocket does not reflect in the Docs. Although the OpenAPI doc added is the 3.0 version which should be able to document websocket endpoints.

[philipokiokio]

@Kludex I don't get the reason you are sending emojis such as the down thumb and all. it's better to ignore than act funny.

[Kludex]

I sent emojis to show how I feel about your comments. I didn't mean to offend you.

Let me explain why:

Truthfully the WebSocket fix works in development (Uvicorn server), however, in production (Ubuntu environment) the websocket did not connect to the APIRouter specified.

There can't be a possible scenario on which it has a different behavior depending on the environment (prod vs dev) because of this issue. It can be because of other factors, but not because of this one.

Another thing I noticed is that the WebSocket does not reflect in the Docs. Although the OpenAPI doc added is the 3.0 version which should be able to document websocket endpoints.

This comment is not true. OpenAPI docs doesn't support WebSockets. On OpenAPI 3.1 Webhooks were added, but there was never support for WebSockets. AsyncAPI is an alternative for WebSockets, but FastAPI doesn't support it.

In any case, it's always better to open a new issue than engaging on a closed issue. It avoids users to believe the issue was wrongly closed.

[philipokiokio]

@Kludex Thanks for your explanation.

To be fair I was not even pointing to this issue, and I agree that it could be something else. I was just bringing it forward (hoping) someone had experienced that and there is a fix to it.

With regards to OpenAPI documentation, thank you for clarifying that, I read it somewhere and I believed it (I also saw the OpenAPI swagger package on PyPI that suggested something along that line).

Thank you for your reply and all you do in the FastAPI community.

Continue to have an awesome day.

[Hyperx837]

same issue in fastapi==0.79.0

[philipokiokio]

Hey @Hyperx837 yeah. You should consider creating another instance of the FastAPI application, create a WebSocket with the newly created app instance and then mount it on the Base App where the core application routers live.

[hscspring]

same issue in fastapi==0.88.0

i should use FastAPI instead of APIRouter....

---

update

ok, it works, well in two files.

If all in one file, should like this order:

router = APIRouter(prefix="/ws")

@router.websocket("/asr")
async def websocket_a(ws_a: WebSocket):...

app = FastAPI()
app.include_router(router)

not this:

router = APIRouter(prefix="/ws")
app = FastAPI()
app.include_router(router)


@router.websocket("/asr")
async def websocket_a(ws_a: WebSocket):...

@Hyperx837 u could have a try

[Lopofsky]

@hscspring thank you so much for your clear reply!

That was the solution for me: replaced @router.websocket_route with @router.websocket then added a prefix to the APIRouter object and ws worked again.

[papapumpnz]

@Lopofsky what FastAPI version are you using? This is not working for me with 0.97.0. Getting the 403 error with websocket endpoints defined in other routes files. Using @router.websocket as well.

[Lopofsky]

@papapumpnz fastapi==0.95.2

[usenet506]

after update 0.95 to 0.100.1, I fix this problem

[AntonOfTheWoods]

I'm still getting this with 0.101.0. Everything works if I app.add_websocket_route("/api/v1/ws/ws", chatroom_ws) but not if I add with a router

[lewisjr]

I confirm with @AntonOfTheWoods . Currently (22 Aug 2023 at 17:20 UTC) the latest version of FastAPI is 0.101.1 which is the version I am using. I updated from 0.97.1 which I was using where I was not able to add a websocket via router. Here is how I have it working in v0.101.1 (barebones):

old code

chat_ws.py

from fastapi import APIRouter, WebSocket

chat_socket = APIRouter()

@chat_socket .websocket("/chat")
async def handle_ws(ws: WebSocket):
    await ws.accept()

    while True:
        string = await ws.receive_text()
        await websocket.send_text(string)

main.py

from fastapi import FastAPI
from . import chat_socket

app = FastAPI()

app.add_websocket_route("/ws", chat_socket)

Edit

Turns out my previous code was wrong, the prefix has to be the same on both the include statement and in the router code. This is for v0.101.0 - v0.101.1. Furthermore, you cannot have route params for this implementation, it will not recognise the route and give you a 403 Error. That being said, if you want to split your websocket code into different modules and have no need to use route params, the working version of it is below:

chat_ws.py

from fastapi import APIRouter, WebSocket

chat_socket = APIRouter()

@chat_socket .websocket("/chat")
async def handle_ws(ws: WebSocket):
    await ws.accept()

    while True:
        string = await ws.receive_text()
        await websocket.send_text(string)

main.py

from fastapi import FastAPI
from . import chat_socket

app = FastAPI()

app.add_websocket_route("/chat", chat_socket)

[annisat]

Reporting this issue with version==0.103.2.
Following @lewisjr 's instruction I changed the route to the same. But postman still says it cannot connect to the url.
Sorry, false alarm. I wrapped another route prefix and I didn't notice it.

[AleksaMCode]

I had the same error when using Python v3.10.7 with FastAPI v0.104.1. Replacing @router.websocket_route with @router.websocket fixed the issue for me. Here is a sample code that works:

• websocket method in ws/ws.py

from fastapi import WebSocket, APIRouter

router = APIRouter(
    prefix="/ws"
)

@router.websocket("/pub/{channel_id}")
async def ws_endpoint(websocket: WebSocket):
    # ...

• main

import uvicorn
from fastapi import FastAPI
from ws import ws

app = FastAPI()
app.include_router(ws.router)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

[Kludex]

This was solved years ago, if you encounter a similar issue, please open a discussion.