Can alternative technologies or protocols that enable bidirectional communication between client and server, similar to WebSocket, be called?

Yes, besides WebSocket, there are other technologies and protocols that provide bidirectional communication between the client and server:

• Server-Sent Events (SSE) — a one-way channel from server to client, but with the possibility of periodic requests from the client.
• HTTP/2 and HTTP/3 with push support — allow the server to send data to the client without an explicit request.
• MQTT — a lightweight messaging protocol supporting subscription and publication, often used in IoT.
• gRPC with streaming support — allows establishing bidirectional data streams.
• Long Polling — a technique where the client keeps an HTTP request open for a long time, and the server responds when data appears.

Each of these options has its own features and is suitable for different scenarios, but WebSocket remains the most versatile for full-duplex real-time communication.