WebSocket connection fails: did not receive a valid HTTP response #1655
Description
Attempts to connect to a WebSocket server, served by FastAPI using the websockets package, fail. But it connects perfectly using aiohttp or wscat(npm) to the same server.
A simple server:
from fastapi import FastAPI, WebSocket
app = FastAPI()
@app.websocket("/ws")
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}")
A simple client:
import asyncio
import websockets
async def main():
uri = "ws://localhost/ws"
async with websockets.connect(uri) as ws:
await ws.send("hello")
print(await ws.recv())
asyncio.run(main())
The error:
➜ python main.py
Traceback (most recent call last):
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\http11.py", line 241, in parse
status_line = yield from parse_line(read_line)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\http11.py", line 309, in parse_line
line = yield from read_line(MAX_LINE_LENGTH)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\streams.py", line 46, in read_line
raise EOFError(f"stream ends after {p} bytes, before end of line")
EOFError: stream ends after 0 bytes, before end of line
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\client.py", line 301, in parse
response = yield from Response.parse(
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\http11.py", line 243, in parse
raise EOFError("connection closed while reading HTTP status line") from exc
EOFError: connection closed while reading HTTP status line
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "X:\Project\Project-431agent\main.py", line 228, in <module>
asyncio.run(main())
File "X:\Program Files\Python312\Lib\asyncio\runners.py", line 194, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "X:\Program Files\Python312\Lib\asyncio\runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "X:\Program Files\Python312\Lib\asyncio\base_events.py", line 687, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "X:\Project\Project-431\agent\main.py", line 224, in main
async with websockets.connect(uri) as ws:
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\asyncio\client.py", line 587, in __aenter__
return await self
^^^^^^^^^^
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\asyncio\client.py", line 543, in __await_impl__
await self.connection.handshake(
File "X:\Users\SandBoxUser\AppData\Roaming\Python\Python312\site-packages\websockets\asyncio\client.py", line 114, in handshake
raise self.protocol.handshake_exc
websockets.exceptions.InvalidMessage: did not receive a valid HTTP response