4.9 - Client Server Model

Question 1

What is a simple description of the client server model?

Answer 1

Clients send request messages to servers, which reply to the clients with response messages.

Question 2

What is an API?

Answer 2

An API (application programming interface) is a set of protocols relating to how different applications communicate with each other. They define how interaction between the applications should be carried out, allowing applications to make use of other applications.

Question 3

What is the websocket protocol?

Answer 3

The websocket protocol is an example of an API which operates in the application layer of the TCP/IP stack. The protocol can be used to provide a constant stream of information between two devices, usually a client’s web browser and a server.

The connection created by the websocket protocol is full-duplex, meaning that data can be transmitted in both directions at the same time.

The websocket protocol, which allows for fast transmission of data by reducing the size of packet headers is used in video streaming, online games and instant messaging

Question 4

What is CRUD?

Answer 4

CRUD is an acronym for :
- Create
- Receive
- Update
- Destroy

Question 5

What is REST?

Answer 5

REST is an acronym for:
- REpresentational
- State
- Transfer

It is a design methodology for online database applications that are queried with a web browser.

Question 6

What are the four HTTP request methods used by REST?

Answer 6

• POST
• GET
• PUT
• DELETE

Question 7

How does a client connect to a database?

Answer 7

1. Client-Server request made by the client to the web browser
2. Web Browser responds with the requested web page (which is delivered as a text file)
3. This text file contains JavaScript which loads an API. The API uses REST to enable the database server to be queried by the client with the use of HTTP request methods
4. The client sends HTTP requests to the database server.
5. The database server responds to the clients requests using either JSON or XML.

6.The clients browser processes the JSON or XML and displays the response to the user.

Question 8

JSON vs XML

Answer 8

• JSON is more compact, easier to read, easier to create and faster for computers to process than XML.
• JSON can also be directly converted to Javascript or Python
• XML is seen to be more flexible than JSON however

Question 9

What are thin client networks?

Answer 9

In Thin client networks, majority of the network’s processing power belongs to servers which provide services and resources including storage and processing.

Its easy to add new clients to Thin Client Networks and the clients are relatively inexpensive machines.

Thin Clients have greater centralised control of the network as software updates and security can be managed from the server.

The servers themselves need to be powerful and thus can be expensive to purchase and require expertise to set up and maintain.

Question 10

What are thick client networks?

Answer 10

In Thick Client Networks, the clients are powerful enough to provide their own processing power and storage. This means there is no need for a server.

They are harder to maintain as there are no servers to issue updates and manage security from a central server.

Thick Clients have much quieter communication channels and have lower likelihoods of data collisions.