WebSocket connection to an EVM node

This article applies to:

• Ethereum
• Polygon
• BNB Smart Chain
• Avalanche
• Fantom
• Harmony

Difference between HTTP and WebSocket protocols

HTTP is unidirectional while WebSocket is bidirectional.

In client-server communication, each HTTP request from the client establishes a new connection and gets closed on receiving a response from the server.

In client-server communication, a WebSocket connection is made once and reused until either the server or the client terminates the connection.

Proper use of WebSocket to connect to an EVM node

When using WebSocket to connect to an EVM node, the recommendation is to open a connection and send requests over the open connection instead of opening a new connection like with HTTP requests.

Reusing the same open connection with WebSocket prevents the EVM node connection pool from running out.

Incorrect usage example with web3.py:

def getLatestBlock():
    web3 = Web3(Web3.WebsocketProvider('wss://ws-nd-123-456-789.p2pify.com/3c6e0b8a9c15224a8228b9a98ca1531'))
    return web3.eth.blockNumber
getLatestBlock()

This example creates a new connection for each getLatestBlock request and keeps the connection open but never used again.

Correct usage example with web3.py:

web3 = Web3(Web3.WebsocketProvider('wss://ws-nd-123-456-789.p2pify.com/3c6e0b8a9c15224a8228b9a98ca1531'))
def getLatestBlock():
    return web3.eth.blockNumber
getLatestBlock()

This example creates one connection and reuses it for each getLatestBlock request.

See also:

• EVM node connection: HTTP vs WebSocket
• Development tools:
  • Ethereum development tools
  • Polygon development tools
  • BNB Smart Chain development tools
  • Avalanche development tools
  • Fantom development tools