WebSocket is a communication protocol that facilitates real-time, bidirectional data exchange over a single, persistent TCP connection, commonly used in applications such as chat, gaming, and IoT. It begins with an HTTP/HTTPS handshake, upgrading to the WebSocket protocol, allowing text and binary data formats with a lightweight framing mechanism for data transfer. Despite its advantages, WebSockets face challenges such as proxy/firewall limitations, scalability issues due to persistent connections, and security vulnerabilities that require measures like SSL/TLS encryption. Various libraries, including Socket.IO and SignalR, help implement WebSockets by offering features like automatic reconnection and fallback options. While WebSockets provide efficient real-time communication, alternatives such as long polling may be more reliable and scalable in certain environments, as highlighted by PubNub, which uses long polling to ensure reliability and scalability across diverse networking conditions. PubNub offers a platform for real-time communication, supporting features like in-app chat and push notifications, and is positioned as a scalable solution with a global presence and high reliability, making it suitable for applications needing real-time data.