WebSocket.

also: WebSockets · websocket · websockets · web socket

A protocol that upgrades an HTTP connection into a long-lived, two-way channel, so server and client can push messages any time.

the two-minute refresher

Starts as an HTTP request with an Upgrade header, then stays open as a full-duplex connection.
Use it for chat, live dashboards, multiplayer games and in-app notifications.
Scaling is the hard part: millions of open connections, and you must route messages to the server holding a user's socket.
For one-way server push, Server-Sent Events are simpler.

also: WebSockets · websocket · websockets · web socket

A protocol that upgrades an HTTP connection into a long-lived, two-way channel, so server and client can push messages any time.

Starts as an HTTP request with an Upgrade header, then stays open as a full-duplex connection.
Use it for chat, live dashboards, multiplayer games and in-app notifications.
Scaling is the hard part: millions of open connections, and you must route messages to the server holding a user's socket.
For one-way server push, Server-Sent Events are simpler.