Calculator Server

Task

Implement an HTTP server with a calculator endpoint that adds two numbers.

• Parse the HTTP request to extract the path and query parameters
• If the path is /add, extract parameters a and b
• Return the sum as a string (e.g., “8” for 5+3)

Function Signature

void handle_request(char *request, int client_socket);

Request Format

An HTTP request line looks like:

GET /add?a=5&b=3 HTTP/1.1

The query parameters are after the ?:

• a=5 means parameter a has value 5
• b=3 means parameter b has value 3
• Parameters are separated by &

HTTP Response Format

Your response should include:

HTTP/1.1 200 OK\r\n
Content-Type: text/plain\r\n
\r\n
<result as string>

Notes

• Use strstr() to find "a=" and "b=" in the request
• Use atoi() to convert string numbers to integers
• Use sprintf() or snprintf() to convert the result back to a string
• Include <string.h> for string functions and <stdlib.h> for atoi()

---

Example

Request Path	Response Body
GET /add?a=5&b=3 HTTP/1.1	8
GET /add?a=10&b=20 HTTP/1.1	30
GET /add?a=0&b=0 HTTP/1.1	0
GET /add?a=100&b=50 HTTP/1.1	150

Test Locally

$ gcc -o calculator_server calculator_server.c http-server.c
$ ./calculator_server
Server started on port 8000
 
# In another terminal:
$ curl "http://localhost:8000/add?a=5&b=3"
8
$ curl "http://localhost:8000/add?a=10&b=20"
30
$ curl "http://localhost:8000/add?a=100&b=50"
150

---

Code

#include "http-server.h"
#include <string.h>
#include <stdlib.h>
 
void handle_request(char *request, int client_socket)
{
    char header[] = "HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\n\r\n";
    if(strncmp(request, "GET /add?", 9) == 0){
        char* start = strstr(request, "?") + 1;
 
        char* a = strstr(start, "a=") + 2;
        char* b = strstr(start, "b=") + 2;
        int a_val = 0;
        int b_val = 0;
        sscanf(a, "%d", &a_val);
        sscanf(b, "%d", &b_val);
 
        int sum = a_val + b_val;
        char result[32];
        sprintf(result, "%d", sum);
        send(client_socket, header, strlen(header), 0);
        send(client_socket, result, strlen(result), 0);
    }
}