Socket.IO is an open-source library that allows real-time communication between a web client and a server. It's used to create event-driven web applications.
Socket.IO establishes connections using low-level transports
WebSocket
WebTransport
HTTP long-polling
Socket.IO stores queued messages when a connection is lost and sends them all at once when the connection is reestablished
The volatile flag can be used to prevent Socket.IO from sending queued messages when a connection is reestablished
How WebSocket Works
Handshake: A WebSocket connection begins with an HTTP request (Upgrade request), which switches the protocol from HTTP to WebSocket.
Connection Establishment: If the server accepts the request, it sends an HTTP 101 status code (Switching Protocols) to the client.
Data Exchange: Once connected, both client and server can send messages asynchronously.
Connection Termination: The connection remains open until either the client or server closes it, or if there is a network failure.
Since WebSockets maintain a persistent connection, they can be affected by:
Server restarts
Network failures
Client disconnects
Timeout issues
To handle reconnections:
Detect if the connection is closed.
Use an exponential backoff mechanism to prevent frequent reconnection attempts.
Implement a ping-pong heartbeat to detect and prevent stale connections.
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