Event Queues :

Much of the NodeJS architecture is built around the use of events. All objects that emit events in NodeJS are instances of the EventEmitter constructor. EventEmitter’s are a great way to handle controlling asynchronous events. Functions can be registered as listeners for an event on instances of the EventEmitter class. These instances can emit events and pass the listener’s data.

OSI Model

Open Systems Interconnection Reference Model” (OSI model) was developed as a seven layer model. This seven layer OSI model has continued to accurately describe the different processes in computer networking, and is still widely used as a point of reference while working in networked systems today. A developer or engineer is usually responsible for the goals of a specific layer and communicating with the layer above and below. Not every computer network solution uses all seven layers, for example HTTP skips the Presentation and Session layers and lives directly on top of the Transport layer.

Internet Protocol Suite

The Internet Protocol Suite is the conceptual model for the protocols used by the internet. It is often referred to as TCP/IP because the IP and TCP were the original protocols in the suite. The Internet Protocol Suite is described using four layers - Link, Internet, Transport, and Application. Web developers often reference the Internet Protocol Suite model when discussing network communication and data exchange.

TCP

The Transmission Control Protocol (TCP) is widely used by application layer protocols in the Internet Protocol Suite. TCP creates a two way communication between two hosts and provides reliable, ordered, and error checked byte streams between the applications. TCP data transfers manage network congestion and use flow control to limit the rate a sender transfers data to guarantee reliable delivery. Each IP packet between the hosts carries a single TCP Segment. A TCP segment is made up of header and data sections.

Connection Establishment

The client sends a SYN packet with an random initial sequence number. The server sends a SYN-ACK packet with the acknowledgment number set to one more than the initial sequence number. The client responds with an ACK and an acknowledgment number incremented by one.