APIs and client server - paper 2 Flashcards
(24 cards)
what are APIs
- a set of protocols that governs how two applications should interact with one another.
- An API sets out the format of requests and responses between a client and a server and enables one application
to make use of the services of another.
limits of HTTP communication
The client must send a request to the server to receive data.
If too much time passes without activity after a socket connection is established,
The server closes (drops) the connection to save resources.
When this happens, the server often sends an error message (like a timeout).
Bandwidth overhead: HTTP headers add extra data, increasing bandwidth usage.
Latency: Each request-response cycle can cause delays, especially over slow networks.
Text-based: Less efficient for binary data compared to some other protocols.
web CRUD applications
NAME → HTTP request method → SQL command
Create → POST → INSERT
Retrieve → GET → SELECT
Update → PUT → UPDATE
Delete → DELETE → DELETE
what is REST
Representational State Transfer is a software architectural style for designing networked applications
examples of APIs
JSON - similar to python dictionary
XML - similar format to html files
advantages of JSON
- more compact so requires less storage, so quicker to transmit and process
- easier to read, write, and maintain
- data clearly defined as objects
disadvantages of JSON
- only works with a limited range of data types
Less secure: Can be vulnerable to injection if not properly handled.
Text-based: Larger in size compared to binary formats like Protocol Buffers.
Parsing errors: Small syntax mistakes (like missing commas) can break the whole file.
No support for comments: Can’t add explanations directly in the data.
advantages of XML
Human-readable and machine-readable: Easy to understand and process by both people and programs.
Platform-independent: Works across different systems and technologies.
Flexible structure: Can represent complex data types
Supports custom tags: Allows users to define their own tags for specific needs.
Widely supported: Many tools and languages have built-in XML support.
Facilitates data sharing: Great for exchanging data between different applications.
disadvantages of XML
expensive use of tags makes it hard to follow
Slower processing: More complex to parse than formats like JSON.
Higher bandwidth usage: Large file size means more data to transfer.
Harder to write manually: Tedious and error-prone without tools.
Not ideal for data storage: Inefficient for large datasets or frequent read/writes.
describe what thin- client computing is
- processing is carried out on a server
- Minimal local processing: Most of the computing is done on a central server, not the client device.
Relies on network connection: Needs a stable connection to access applications and data.
Lightweight hardware: Thin clients can be low-power devices (e.g., terminals, Chromebooks).
Centralised management: Easier to update, secure, and maintain systems from the server.
Common in businesses: Used in environments like schools, offices, and call centres.
how does the client - server model work
- a client will send a request message to a server
- which should respond with the data requested or a suitable message otherwise.
a distributed application structure where clients request services from servers
example of a client - server model
Client (e.g. browser) sends a request for a web page.
The server receives the request and finds the needed page/data.
The server sends back a response with the web page content.
The browser displays (renders) the web page on the user’s screen.
This is how many websites work using the client-server model.
examples of server types
File server
Email server
FTP server
Proxy server
DHCP server
Print server
Database server
What is the WebSocket API protocol used for?
It establishes a persistent, full-duplex connection over TCP between a browser and a server, allowing real-time, two-way communication.
Reduced header information, increasing data transfer speed; and reducing load on server
Connecting a database to a browser with HTTP request methods
User interacts with browser: e.g., submits a form or clicks a button.
Browser sends HTTP request: Using methods like:
GET – to fetch data (e.g., view products).
POST – to send new data (e.g., submit a form).
PUT/PATCH – to update existing data.
DELETE – to remove data.
Server receives request: Backend processes the request using code (e.g., Python, Node.js, PHP).
Server interacts with database: Sends SQL queries to retrieve, insert, update, or delete data.
Server sends HTTP response: Returns data (usually in JSON) or confirmation to the browser.
Browser updates UI: Based on the server’s response (e.g., shows new content or success message)
advantages of thin client
- Easy to set up, maintain and add
terminals to a network with little installation required locally - Software and updates can be installed
on the server and automatically distributed to each client terminal - More secure since data is all kept centrally in one place
disadvantages of thin client
- Reliant on the server, so if the server
goes down, the terminals lose functionality - Requires a very powerful, and reliable
server which is expensive - Server demand and bandwidth increased as they rely on server for most tasks.
- Maintaining network connections for
portable devices consumes more battery power than local data processing
advantages of thick client
- Robust and reliable, providing greater
up-time - Can operate without a continuous
connection to the server - Generally better for running more
powerful software applications
Application performance can be faster in thick clients because they don’t rely on network latency.
disadvantages of thick client
- More expensive, higher specification
client computers required - Installation of software required on
each terminal separately and network administration time is increased - Integrity issues with distributed data
harder to update, more complex installs.
how does thin client computing work
- Client terminals load operating system from server at start up;
- Applications installed on server and accessed remotely by terminals;
- Client (dumb) terminals act as interfaces only;
- All processing is done by the server
Give a real-world example of when WebSocket would be preferred over HTTP.
Real-time chat apps, multiplayer games, or live trading dashboards.
What is a full-duplex connection?
A connection where both parties can send and receive data simultaneously.
How does REST allow JavaScript to communicate with a server?
JavaScript uses HTTP methods (like GET, POST) to send requests to the server’s REST API, which processes the request and responds with data.
What is the difference between thin and thick client computing?
Thin clients rely on the server for processing, while thick clients perform processing locally.
