Web3.py AsyncWeb3 WebSocket Connection Fails for Infura Sepolia

Question

I’m working on an Ethereum project that connects to the Sepolia network using Infura's WebSocket endpoint (wss://sepolia.infura.io/ws/v3/<PROJECT_ID>). While the connection works fine in Postman, my Python implementation using Web3.py fails with the following error:

ERROR:BlockchainLayer:Error connecting to WebSocket: Could not connect to: wss://sepolia.infura.io/ws/v3/<PROJECT_ID>. Retries exceeded max of 5.

I tried applying ExtraDataToPOAMiddleware as I did with the HTTP connection, since Sepolia uses a Proof-of-Authority (PoA) consensus, but no luck. The same setup works perfectly for the HTTP endpoint, but WebSocket connections keep failing.

Here is the relevant code for the WebSocket connection:

async def connect_websocket(self):
    """
    Connects to the WebSocket endpoint using AsyncWeb3 and manages its context.
    """
    try:
        async with AsyncWeb3(WebSocketProvider(self.websocket_url)) as w3:
            # w3.middleware_onion.inject(ExtraDataToPOAMiddleware, layer=0)
            self.web3_ws = w3  
            if not await self.web3_ws.is_connected():
                raise ConnectionError(f"Failed to connect to WebSocket endpoint: {self.websocket_url}")
            self.logger.info(f"Connected to {self.network_name} network via WebSocket.")
    except ConnectionClosedError as e:
        self.logger.error(f"WebSocket connection closed: {e}")
    except Exception as e:
        self.logger.error(f"Error connecting to WebSocket: {e}")

What I’ve Tried

Verified the WebSocket endpoint using Postman, and it responds with 101 Switching Protocols.
Confirmed the API key and URL are correct.
Applied ExtraDataToPOAMiddleware for PoA compatibility.
Tested rate-limiting settings and ensured the free-tier limits are not exceeded.
Updated Web3.py to the latest version available.

Any insights or examples of working implementations would be greatly appreciated!

seddouguim · Accepted Answer · 2024-12-14 04:52:27Z

It turned out the issue was an [SSL: CERTIFICATE_VERIFY_FAILED] error, but I didn’t realize it at first because my logger wasn’t set up early enough in the code. The error wasn’t showing up in the logs, so I had no idea what was going wrong. Once I moved the logger initialization to the very start of my __init__ method, the issue became clear.

On macOS, the fix was to install the proper SSL certificates. Here’s what worked for me:

Installed certifi with Homebrew to get a fresh set of certificates:
```
brew install certifi
```

Set up the environment variables to point to the certificates:

export SSL_CERT_FILE=/opt/homebrew/etc/[email protected]/cert.pem
export SSL_CERT_DIR=/opt/homebrew/etc/[email protected]/

Made the changes permanent by adding them to ~/.zshrc:

echo "export SSL_CERT_FILE=/opt/homebrew/etc/[email protected]/cert.pem" >> ~/.zshrc
echo "export SSL_CERT_DIR=/opt/homebrew/etc/[email protected]/" >> ~/.zshrc
source ~/.zshrc

After that, everything worked smoothly.

If you’re on Windows or Linux, the solution might be a little different. On Windows, you might need to run the Install Certificates.command file that comes with Python. On Linux, you might need to install certificates with your package manager, like:

sudo apt install ca-certificates

or

sudo yum install ca-certificates

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