First API request and response in Rest API - Step-by-Step Execution

Concept Flow - First API request and response

Start

↓

Create HTTP Request

↓

Send Request to Server

↓

Server Processes Request

↓

Server Sends HTTP Response

↓

Receive Response

↓

Read Status and Data

↓

End

This flow shows how a client sends a request to a server and waits for the server's response.

Execution Sample

Rest API

GET /api/hello HTTP/1.1
Host: example.com


Response:
HTTP/1.1 200 OK
Content-Type: application/json

{"message": "Hello, world!"}

This example sends a GET request to /api/hello and receives a JSON message in response.

Execution Table

Step	Action	Details	Result
1	Create HTTP Request	Method: GET, URL: /api/hello, Host: example.com	Request ready to send
2	Send Request	Request sent over network to server	Waiting for response
3	Server Receives Request	Server reads GET /api/hello	Server processes request
4	Server Sends Response	Status: 200 OK, Content-Type: application/json	Response sent back
5	Client Receives Response	Reads status and headers	Status 200 OK confirmed
6	Client Reads Body	Body: {"message": "Hello, world!"}	Message extracted
7	End	Request-response cycle complete	Client has data to use

💡 Response received with status 200 OK, cycle ends successfully

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 5	After Step 6	Final
request	None	GET /api/hello with Host header	Sent over network	N/A	N/A	N/A
response_status	None	None	None	200 OK	200 OK	200 OK
response_headers	None	None	None	Content-Type: application/json	Content-Type: application/json	Content-Type: application/json
response_body	None	None	None	None	{"message": "Hello, world!"}	{"message": "Hello, world!"}

Key Moments - 3 Insights

Why do we need to include the Host header in the request?

The Host header tells the server which website or service we want, especially if the server hosts many sites. See Step 1 in the execution_table where the Host header is set.

What does the status code 200 OK mean in the response?

It means the request was successful and the server is sending back the requested data. This is shown in Step 5 where the client reads the status 200 OK.

Why do we read the response body after the headers?

Headers tell us about the data type and length, so we know how to handle the body. Step 6 shows reading the body after confirming headers.

Visual Quiz - 3 Questions

Look at the execution_table, what is the status code received at Step 5?

A 500 Internal Server Error

B 404 Not Found

C 200 OK

D 301 Moved Permanently

💡 Hint

Check the 'response_status' column in variable_tracker after Step 5

At which step does the client send the request to the server?

A Step 2

B Step 1

C Step 4

D Step 6

💡 Hint

Look at the 'Action' column in execution_table for sending the request

If the server responded with status 404, which step would show a different result?

A Step 3 - Server Receives Request

B Step 4 - Server Sends Response

C Step 6 - Client Reads Body

D Step 7 - End

💡 Hint

Check the 'Details' and 'Result' columns in Step 4 for response status

Concept Snapshot

First API request and response:
- Client creates HTTP request (method, URL, headers)
- Request sent to server
- Server processes and sends HTTP response (status, headers, body)
- Client receives and reads status, headers, then body
- Status 200 means success
- Host header specifies target server

Full Transcript

This visual trace shows how a client makes its first API request and receives a response. The client builds an HTTP GET request with a Host header and sends it to the server. The server processes the request and replies with a status code 200 OK and a JSON message body. The client reads the status and headers first, then the body. This cycle completes the request-response interaction, which is the foundation of REST APIs.

Practice

1. What does a GET request in an API usually do?

easy

A. It asks the server to send data back.

B. It sends data to the server to be saved.

C. It deletes data from the server.

D. It updates existing data on the server.

Solution

1. Step 1: Understand the GET method

   The GET method is used to request data from a server without changing it.

2. Step 2: Identify the purpose of GET in API

   GET asks the server to send data back to the client.

3. Final Answer:

   It asks the server to send data back. -> Option A

4. Quick Check:

   GET = Request data [OK]

Hint: GET means get data from server, no changes made [OK]

Common Mistakes:

• Confusing GET with POST or DELETE methods
• Thinking GET changes data on server
• Mixing up request and response roles

2. Which of these is the correct way to write a simple GET request URL?

easy

A. POST /api/data HTTP/1.1

B. DELETE /api/data HTTP/1.1

C. GET /api/data HTTP/1.1

D. PUT /api/data HTTP/1.1

Solution

1. Step 1: Identify HTTP methods

   GET is the method used to request data, so the request line must start with GET.

2. Step 2: Check the request format

   The correct format is "GET /path HTTP/1.1" for a GET request.

3. Final Answer:

   GET /api/data HTTP/1.1 -> Option C

4. Quick Check:

   GET request line starts with GET [OK]

Hint: GET requests start with GET keyword in HTTP line [OK]

Common Mistakes:

• Using POST, DELETE, or PUT instead of GET
• Wrong HTTP version or missing method
• Confusing request line with response line

3. Given this API response snippet:

{"status":200,"data":{"name":"Alice","age":30}}

What does the status code 200 mean?

medium

A. The request was unauthorized.

B. The requested resource was not found.

C. There was a server error processing the request.

D. The request was successful and data is returned.

Solution

1. Step 1: Understand HTTP status codes

   Status code 200 means the request succeeded and the server returned the requested data.

2. Step 2: Match status code to meaning

   200 is standard for success; 404 means not found, 500 means server error, 401 means unauthorized.

3. Final Answer:

   The request was successful and data is returned. -> Option D

4. Quick Check:

   Status 200 = Success [OK]

Hint: 200 means OK, request worked fine [OK]

Common Mistakes:

• Confusing 200 with error codes like 404 or 500
• Thinking 200 means no data returned
• Mixing status codes with data content

4. You send a GET request to an API but get no response. Which of these is a likely cause?

medium

A. The server returned status code 200.

B. The API endpoint URL is incorrect or misspelled.

C. You used the GET method instead of POST.

D. Your request included a valid Authorization header.

Solution

1. Step 1: Check the URL correctness

   If the URL is wrong or misspelled, the server won't respond properly or may not be found.

2. Step 2: Evaluate other options

   Using GET instead of POST may cause wrong data but usually gets a response; status 200 means success; valid Authorization helps access.

3. Final Answer:

   The API endpoint URL is incorrect or misspelled. -> Option B

4. Quick Check:

   Wrong URL = No response [OK]

Hint: Check URL spelling first if no response [OK]

Common Mistakes:

• Assuming method error causes no response
• Ignoring URL typos
• Confusing status codes with no response

5. You want to get user info from an API at https://api.example.com/users/123. Which is the best way to check if your request worked?

hard

A. Check if the response status code is 200 and the data contains user details.

B. Check if the request method was POST and the server returned 404.

C. Check if the response status code is 500 and the data is empty.

D. Check if the URL contains the word 'users' and the method is DELETE.

Solution

1. Step 1: Understand success criteria for API requests

   A successful GET request returns status 200 and the expected data.

2. Step 2: Evaluate options for correctness

   POST method and 404 means not found; 500 means server error; DELETE method is for removing data, not getting it.

3. Final Answer:

   Check if the response status code is 200 and the data contains user details. -> Option A

4. Quick Check:

   Status 200 + data = success [OK]

Hint: Success = status 200 + expected data [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Ignoring status codes meaning
• Checking wrong HTTP methods for GET requests