WebSocket service always closes the connection after receiving a message from the client when connecting through Azure API Management

Question

I deployed a WebSocket service on Azure Kubernetes. It's worked fine if connect to the service directly, but when I try to connect my service through API Management. It always closes the connection after receiving a message from the client.

Service Code:

from fastapi import FastAPI, Request, Header, Response  
from fastapi import WebSocket, WebSocketDisconnect, Query  
from fastapi.middleware.cors import CORSMiddleware  
  
from pathlib import Path  
  
import os  
import time  
import websockets  
import logging  
  
from custom_logging import CustomizeLogger  
  
app = FastAPI()  
app.add_middleware(  
    CORSMiddleware,  
    allow_origins=["*"],  
    allow_credentials=True,  
    allow_methods=["*"],  
    allow_headers=["*"],  
)  
  
# logger = logging.getLogger(__name__)  
config_path=Path(__file__).with_name("log_config.json")  
logger = CustomizeLogger.make_logger(config_path)  
  
@app.websocket("/ws")  
async def websoc(websocket: WebSocket):  
    await websocket.accept()  
    try:  
        while True:  
            msg = await websocket.receive_text()  
            logger.info('recieve:'+ msg)  
  
            await websocket.send_text(msg)  
          
    except Exception as e:  
        logger.info(e)  

Client Code

import websockets  
import asyncio  
import time  
  
async def send_receive():  
    async with websockets.connect(  
        'wss://xxxx.azure-api.net/testwebsocket?subscription-key=xxx',   
                                  ping_interval=5,  
                                  ping_timeout=20) as websocket:  
        for i in range(10):  
            await websocket.send(str(i))  
            await asyncio.sleep(0.1)  
            msg = await websocket.recv()  
            print(msg)  
          
asyncio.run(send_receive())  

Result from my custom log on service when call through API management

Result from my custom log on service when call it directly