ITEC 4020 - L4: Web Services (Concepts)

Web Service

A software system that enables machine-to-machine communication over a network using standardized protocols like HTTP/HTTPS.

Key Traits of Web Services

Platform-independent, interoperable, loosely coupled, and use standardized protocols.

Purpose of Web Services

Allow application integration, reusability, interoperability, and scalability.

Application Integration

Web services connect different systems, such as linking inventory systems with sales systems.

Reusability

A single web service can be reused by multiple applications, like a shared payment API.

Interoperability

Web services allow different platforms and programming languages to work together.

Scalability

Web services can be distributed across multiple servers to handle more users or requests.

Real-World Examples of Web Services

APIs like OpenWeatherMap (weather), Google Maps, PayPal/Stripe (payments), and “Sign in with Google.”

Request-Response Model

The client sends an HTTP request, the server processes it, and replies with a response.

HTTP Request Contains

Method (GET, POST, etc.), URL, headers, and optional body.

HTTP Response Contains

Status code (200, 404), headers, and body (data or error message).

Stateless Communication

Each request is independent, with no memory of previous interactions; default in HTTP.

Stateful Communication

The server maintains context across multiple requests, remembering session data.

Advantage of Stateless Communication

Makes scaling and load balancing easier since no session data is stored on the server.

Advantage of Stateful Communication

Allows features like login sessions or remembering user data across requests.

Examples of Stateful Protocols

Protocols like FTP, Telnet, or traditional database connections.

Cookies

A small piece of client-side data sent with each request to help maintain state in stateless HTTP.

Tokens (JWTs)

A client-stored authentication token sent with requests to maintain secure state.

URL Parameters

Information added to the query string of a URL to carry session or state data.

Custom Headers

Headers added to HTTP requests that carry state information like authentication tokens.

Booking API Example

In a movie booking service, the client POSTs with a token and data, the server validates and processes, and replies with confirmation.