WebSocket is a full-duplex communication protocol that allows for persistent, bidirectional communication between client and server over a single TCP connection.

• HTTP: Request-response model (client initiates).

• WebSocket: Continuous connection (either side can send messages anytime).

• Transport Layer Foundation: TCP is a transport layer protocol that provides reliable, ordered, and error-checked delivery of data between applications. WebSocket is a higher-level protocol that operates on top of TCP, using its reliable connection as the basis for its own communication model.

• Connection Establishment: A WebSocket connection begins with an HTTP handshake that uses the HTTP Upgrade header to switch from HTTP to the WebSocket protocol. Once established, the connection persists as a single TCP connection, enabling ongoing, full-duplex (two-way) communication between client and server.

• Message Framing: While TCP transmits a continuous stream of bytes, WebSockets introduce their own framing mechanism. Data sent over a WebSocket is organized into discrete messages, each with its own frame header, allowing the application to work with complete messages rather than arbitrary byte streams.

• Reliability and Ordering: All WebSocket messages benefit from TCP’s guarantees of reliable and in-order delivery. This is essential for real-time web applications—such as live chat, gaming, and collaborative editing—where message loss or disorder would degrade the user experience.

• Full-Duplex Communication: WebSockets enable both client and server to send data independently and simultaneously over a single TCP connection, unlike HTTP’s request-response model.

• Low Overhead: After the initial handshake, the protocol overhead is minimal, making WebSockets efficient for high-frequency, real-time data exchange.

• Firewall and Proxy Compatibility: By leveraging standard HTTP ports (80 and 443) for the handshake, WebSockets can traverse most firewalls and proxies that would otherwise block custom protocols.