Introduction

This article is Part - I of my 6-article series on Computer Networking, which aims to cover many topics like OSI Model, IP Model, Networking Protocols etc. This article will help you gain knowledge about some basic concepts which you would require in further articles to understand them better.

Basic Concepts

Data is transferred in the form of Packets.
IPv4 Addresses : X - X - X - X where X ranges from 0 to 255. Denotes the location of your computer. To check IP Address of your system, use command :

hostname -i | awk '{print $1}'

Modem/Router converts analog signals into digital signals and vice versa. Routers have a global IP address and assign unique IP Addresses to each device connected to it.
Thread is a lighter version of a process. One process can have multiple running threads.
Client - Server Architecture

Protocols

Protocols are nothing but how data is transferred in a computer network.

TCP(Transmission Control Protocol)
Ensures data will reach its destination and will not be corrupted in the way. Connection-oriented protocol.
UDP(User Datagram Protocol)
Useful in cases where you do not care if 100% data is reaching the destination or not. Stateless and Connection-less protocol. Data may be lost. Used widely in Gaming, Video Conferencing etc.
HTTP(Hyper Text Transfer Protocol)
Used by World Wide Web(WWW) and web browsers.
HTTPS(Hyper Text Transfer Protocol Secure)
Extension of HTTP. Used for secure communication over a computer network. Uses HSTS and TLS for encryption and authentication.
DHCP(Dynamic Host Configuration Protocol)
Network management protocol used on Internet Protocol networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture.
SMTP(Simple Mail Transfer Protocol)
Send and distribute outgoing emails.
POP3 & IMAC
Receive emails.
SSH
Login to a terminal of someone else's computer.
PPP(Point To Point Protocol)
Create a direct connection between two communicating devices. It defines rules using which two devices will authenticate with each other and exchange information.
FTP(File Transfer Protocol)
Transfer files from one system to another. Works on client-server model. When a machine requests for file transfer from another machine, FTP sets up a connection between the two and authenticates each other using ID and password.
SFTP(Secure File Transfer Protocol)
Encrypts both commands and data while in transmission. Encrypts files and sends them over a shell data stream.
TELENET(Terminal Network)
Used for virtual terminal service given by ISO. This enables one local machine to connect with another. The computer being connected is the remote computer and which is connecting is the local computer. TELENET operation lets us display anything being performed on the remote computer in the local computer.

Port Numbers

Port Numbers are 16 Bit Numbers. Denotes which application is to be communicated with in a computer. Denotes which application we are working with.
Total Port Number possible are 2^16 ~ 65,000.
Reserved Ports - 0 to 1023
Reserved for certain types of applications - 1024 to 49152
Remaining ones can be used by you.
Ephemeral Ports
Application internally assigns itself random port numbers. Used internally within the computer. Ex - mutiple tabs in chrome will have different port numbers assigned to them by the browser.
Sockets
Interface between a process and the internet. When you need to send messages from one system to another, sockets can be used.