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

Concept Flow - First API request and response

Start

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Create HTTP Request

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Send Request to Server

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Server Processes Request

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Server Sends HTTP Response

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Receive Response

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Read Status and Data

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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.