34a.c

/*
============================================================================
Name : 34a
Author : Piyush Singh
Description : Write a program to create a concurrent server.
a. use fork
b. use pthread_create
Date: 26th Sep, 2025.
============================================================================
*/

// TCP Concurrent Server using fork()
#include <stdio.h>          // printf(), perror()
#include <stdlib.h>         // exit()
#include <string.h>         // memset()
#include <unistd.h>         // read(), write(), close(), fork()
#include <sys/socket.h>     // socket(), bind(), listen(), accept()
#include <netinet/in.h>     // sockaddr_in, htons(), INADDR_ANY

void handle_client(int client_fd) 
{
    char buffer[1024];

    // Read message from client
    read(client_fd, buffer, sizeof(buffer));
    printf("👶 Child received: %s\n", buffer);

    // Send response to client
    write(client_fd, "👋 Hello from forked server!", 28);

    // Close client socket
    close(client_fd);
}

int main() 
{
    int server_fd, client_fd;
    struct sockaddr_in server_addr;

    // Step 1: Create TCP socket
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd == -1) 
    {
        perror("❌ socket failed");
        exit(1);
    }

    // Step 2: Bind to port 8081
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;  // Accept connections from any IP
    server_addr.sin_port = htons(8081);        // Port number

    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) 
    {
        perror("❌ bind failed");
        exit(1);
    }

    // Step 3: Listen for incoming connections
    listen(server_fd, 5);
    printf("🟢 Fork-based server listening on port 8081...\n");

    // Step 4: Accept and handle clients concurrently
    while (1) 
    {
        client_fd = accept(server_fd, NULL, NULL);
        if (client_fd == -1) 
        {
            perror("❌ accept failed");
            continue;
        }

        // Create a child process to handle the client
        if (fork() == 0) 
        {
            handle_client(client_fd);
            exit(0);  // Child exits after handling
        }

        // Parent closes duplicate client socket
        close(client_fd);
    }

    return 0;
}

/*
Output:
╰─ ./34a                                                                      ─╯
🟢 Fork-based server listening on port 8081...
*/