miguelgrinberg/Flask-SocketIO
Flask SocketIO
Flask-SocketIO is a Flask extension that integrates the Socket.IO real-time communication protocol into Flask applications, enabling persistent bidirectional connections between servers and clients. It transparently switches between WebSocket and HTTP long-polling while maintaining a persistent session identity, and provides a full event-driven framework for real-time web application communication.
The library distinguishes itself with support for namespace multiplexing, allowing event handlers to be isolated into separate namespaces with independent lifecycle and routing. It also offers room-based pub-sub messaging, organizing clients into named groups for efficient targeted broadcasting. Authentication during the connection handshake, cross-origin request restriction, and separate real-time session storage prevent conflicts with HTTP sessions. Additional capabilities include disconnect reason inspection, a request-reply event pattern, wildcard event routing, and the ability to emit events to connected clients from external processes through a shared message queue.
Flask-SocketIO supports horizontal scaling across multiple server instances by using a message queue to synchronize events and session state. It provides access to the Flask application context and authenticated user inside event handlers, along with built-in error handling for event processing.
Features
- Real-Time Web Communication - Provides persistent bidirectional connections for live data exchange in web applications using Socket.IO and Flask.
- Event Stream Broadcasters - Broadcasts real-time events to connected clients with room targeting and optional acknowledgment callbacks.
- Custom Event Broadcasting - Listens for custom events from clients and broadcasts responses to individuals, groups, or all connections.
- Socket Event Synchronization Queues - Synchronizes broadcasts and session state across multiple server instances using a shared message queue.
- Room-Based Message Routing - Organizes connected clients into named rooms and routes messages to targeted subsets for precise delivery control.
- Targeted Client Group Messaging - Organizes connected clients into named groups to send targeted events to specific subsets of users.
- WebSocket and Fallback Connection Establishment - Establishes low-latency persistent bidirectional connections using WebSocket with automatic HTTP long-polling fallback.
- Namespace Multiplexing - Isolates event handlers into separate namespaces with independent lifecycle and event routing for real-time communication.
- Socket Client Lifecycle Event Handlers - Triggers custom logic when a client connects, disconnects, or changes state, with optional authentication and rejection.
- Connection Lifecycle Management - Manages the full lifecycle of socket connections including identity verification, cross-origin requests, and session persistence.
- WebSocket and HTTP Fallback Transports - Switches between WebSocket and HTTP long-polling transparently while maintaining a persistent session identity.
- Room-Based Client Grouping - Organizes clients into named rooms for targeted broadcasting and efficient event delivery to specific groups.
- Room-Based Pub-Sub Broadcasting - Organizes clients into named rooms and broadcasts events to specific groups using a pub-sub mechanism.
- Server Event Handlers - Provides server-side event handler registration for listening to and responding to real-time client events.
- Flask Socket.IO Integrations - Integrates the Socket.IO protocol into the Flask web framework for real-time bidirectional communication.
- Real-Time Frameworks - Establishes persistent bidirectional connections between servers and clients using WebSocket with automatic HTTP fallback.
- Distributed Socket Server Scaling - Distributes real-time connections across multiple server instances using a message queue for coordinated broadcasting.
- Socket Connection - Distributes real-time client connections and events across multiple server instances using a shared message queue.
- Distributed Socket Event Coordination - Uses a shared message queue to synchronize events across multiple worker processes for horizontal scaling.
- External Process Emissions - Emits events from external processes to connected clients through a shared message queue.
- Handshake Credential Validators - Validates client credentials during the handshake using token or other authentication methods before granting channel access.
- Authenticated User Context in Socket Events - Exposes the authenticated user inside event handlers and provides a decorator to disconnect unauthenticated clients.
- Utilities and Helpers - Socket.IO integration.
- Websockets - Listed in the “Websockets” section of the Awesome Python awesome list.
- WebSocket - Socket.IO integration for Flask applications.
