Networking

• Packet - most basic unit of that is transferred over a network, the envelopes that carry your data from one end point to the other

Connecting

In networking, a connection refers to pieces of related information that are transferred through a network.

• LAN (Local Area Network) - A network or portion of a network that is not publicly accessible to the greater internet
• WAN (Wide Area Network) - A network that is more extensive than a LAN

Networking Interface

A network interface may be associated with a physical device or virtual interface.

• Port - An address on a single machine that can tied to a specific piece of software, allows your server to be able to communicate using more than one application
  • each computer can have many services
  • a port is a number between 1 and 65535 that differentiates among the services on a system
• Firewall - A program that decides whether traffic coming into a server or going out should be allowed. Rules for which type of traffic is acceptable on which ports
• NAT (Network Address Translation) - A way to translate requests that are incoming into a routing server to the relevant devices or servers that it knows about in the LAN
• VPN (Virtual Private Network) - A way of connecting separate LANs through the internet, while maintaining privacy. A means of connecting remote systems as if they were on a local network, often for security reasons.

Protocols

A set of rules and standards that define a language that devices can use to communicate.

Any service can listen on any port, but there are customary ports for many protocols:

• 21 - FTP (control port)
• 22 - SSH
• 25 - SMTP
• 80 - HTTP
• 443 - HTTPS
• 3306 - MYSQL
• 5432 - Postgresql
• 5984 - CouchDB
• 6667 - IRC

Ports

• HTTP - browse web pages
• HTTPS - browse web pages with encryption
• SMTP - send and receive emails
• IMAP, POP3 - load emails from an inbox
• IRC - chat
• FTP - file transfer
• SSH - remote shell over an encrypted connection
• SSL - low-level secure data transfer (used by HTTPS)

Protocols cont

the language that computer programs speak to each other with.

Some common protocols:

• Media Access Control - A communications protocol that is used to distinguish specific devices
• IP - One of the fundamental protocols that allow the internet to work. IP addresses are unique on each network and they allow machines to address each other across a network
• ICMP (Internet Control Message Protocol) - Used to send messages between devices to indicate the availability or error conditions
• TCP (Transmission Control Protocol) - Used to establish reliable connections and is implemented in the transport layer of the TCP/IP model
• UDP (User Datagram Protocol) - Popular companion protocol to TCP and is also implemented in the transport layer
• HTTP (Hypertext Transfer Protocol) - A protocol defined in the application layer that forms the basis for communication on the web
• FTP (File Transfer Protocol) - In the application layer and provides a way of transferring complete files from one host to another
• DNS (Domain Name System) - An application layer protocol used to provide a human-friendly naming mechanism for internet resources
• SSH (Secured Shell) - An encrypted protocol implemented in the application layer than be used to communicate with a remote server in a secure way

Protocols cont

Networking works by piggybacking a number of different protocols on top of each other.

any networked computer can be a server

any networked computer can be a client

pieces of data, aka packets sent over the network

TCP - reliable transport, acknowledges packet

UDP - unreliable transport, packets sent but no confirmation

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There are a multiple technologies and protocols that are built on top of each other in order for communication to function more easily. Each successive, higher layer abstracts the raw data a little bit more and makes it simpler to use for applications and users.

• OSI Model
• TCP/IP Model

Network Layers

Open Systems Interconnect

OSI Model

Seven separate layers:

• Application - Layer where the users-applications most often interact with.
• Presentation - Responsible for mapping resources and creating context
• Session - Connection handler, creates, maintains and destroys connections between nodes in a persistent way
• Transport - Responsible for handling the layers above it a reliable connection.
• Network - Used to route data between different nodes on the network
• Data Link - A method of establishing and maintaining reliable links between different nodes or devices on a network using existing physical connections
• Physical - Responsible for handling the actual physical devices that are used to make a connection

Internet Protocol Suite, another layering model that is simpler and widely adopted

TCP/IP Model

Four separate layers:

• Application - Responsible for creating and transmitting user data between applications
• Transport - Responsible for communicating between processess
• Internet - Used to transport data from node to node in a network
• Link - Implements the actual topology of the local network that allows the internet layer to present an addressable interface

What is a Full Stack Developer?

Front End / Client Side

Back End / Server Side

HTTP Request

HTTP Response

• HTML
• CSS
• Javascript
• Front end frameworks (Angular, React)

• Node.js
• Express
• SQL
• Database

• 100s - Informational (issued on a provisional basis while request processing continues)
• 200s - Success (request was received, understood and accepted)
• 300s - Redirection (client must take additional action to complete the request)
• 400s - Client Errors (errors caused by the client)
• 500s - Server Errors (server failed to fulfill a request)

HTTP Status Codes

Hypertext Transfer Protocol (HTTP) status codes are issued by the server in response to a client's request made to the server.

• Chrome Browser
• Text Editor (Visual Studio Code)
• Command Line
• Github
• Git

The Developer Toolkit

Your problem solving tools:

Chrome Browser

Built-In Developer Tools for Debugging

Text Editor

A text editor for code and markup.

Command Line 

Interacting with a computer program

Github

A code hosting platform for version control and collaboration, where developers can store and share their projects. 

What is Git?

A version control system created by Linus Torvalds that allows you and the team to keep track of every modification to the code and allows for easy collaboration with other developers.