Design a concurrent server for handling multiple clients using fork()

// Accept connection request from client in cliAddr
// socket structure
clientSocket = accept(
    sockfd, (struct sockaddr*)&cliAddr, &addr_size);

// Make a child process by fork() and check if child
// process is created successfully
if ((childpid = fork()) == 0) {
    // Send a confirmation message to the client for
    // successful connection
    send(clientSocket, "hi client", strlen("hi client"),
         0);
}

// Server side program that sends
// a 'hi client' message
// to every client concurrently

#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

// PORT number
#define PORT 4444

int main()
{
    // Server socket id
    int sockfd, ret;

    // Server socket address structures
    struct sockaddr_in serverAddr;

    // Client socket id
    int clientSocket;

    // Client socket address structures
    struct sockaddr_in cliAddr;

    // Stores byte size of server socket address
    socklen_t addr_size;

    // Child process id
    pid_t childpid;

    // Creates a TCP socket id from IPV4 family
    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    // Error handling if socket id is not valid
    if (sockfd < 0) {
        printf("Error in connection.\n");
        exit(1);
    }

    printf("Server Socket is created.\n");

    // Initializing address structure with NULL
    memset(&serverAddr, '\0',
           sizeof(serverAddr));

    // Assign port number and IP address
    // to the socket created
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(PORT);

    // 127.0.0.1 is a loopback address
    serverAddr.sin_addr.s_addr
        = inet_addr("127.0.0.1");

    // Binding the socket id with
    // the socket structure
    ret = bind(sockfd,
               (struct sockaddr*)&serverAddr,
               sizeof(serverAddr));

    // Error handling
    if (ret < 0) {
        printf("Error in binding.\n");
        exit(1);
    }

    // Listening for connections (upto 10)
    if (listen(sockfd, 10) == 0) {
        printf("Listening...\n\n");
    }

    int cnt = 0;
    while (1) {

        // Accept clients and
        // store their information in cliAddr
        clientSocket = accept(
            sockfd, (struct sockaddr*)&cliAddr,
            &addr_size);

        // Error handling
        if (clientSocket < 0) {
            exit(1);
        }

        // Displaying information of
        // connected client
        printf("Connection accepted from %s:%d\n",
               inet_ntoa(cliAddr.sin_addr),
               ntohs(cliAddr.sin_port));

        // Print number of clients
        // connected till now
        printf("Clients connected: %d\n\n",
               ++cnt);

        // Creates a child process
        if ((childpid = fork()) == 0) {

            // Closing the server socket id
            close(sockfd);

            // Send a confirmation message
            // to the client
            send(clientSocket, "hi client",
                 strlen("hi client"), 0);
        }
    }

    // Close the client socket id
    close(clientSocket);
    return 0;
}

// Client Side program to test
// the TCP server that returns
// a 'hi client' message

#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

// PORT number
#define PORT 4444

int main()
{
    // Socket id
    int clientSocket, ret;

    // Client socket structure
    struct sockaddr_in cliAddr;

    // char array to store incoming message
    char buffer[1024];

    // Creating socket id
    clientSocket = socket(AF_INET,
                          SOCK_STREAM, 0);

    if (clientSocket < 0) {
        printf("Error in connection.\n");
        exit(1);
    }
    printf("Client Socket is created.\n");

    // Initializing socket structure with NULL
    memset(&cliAddr, '\0', sizeof(cliAddr));

    // Initializing buffer array with NULL
    memset(buffer, '\0', sizeof(buffer));

    // Assigning port number and IP address
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(PORT);

    // 127.0.0.1 is Loopback IP
    serverAddr.sin_addr.s_addr
        = inet_addr("127.0.0.1");

    // connect() to connect to the server
    ret = connect(clientSocket,
                  (struct sockaddr*)&serverAddr,
                  sizeof(serverAddr));

    if (ret < 0) {
        printf("Error in connection.\n");
        exit(1);
    }

    printf("Connected to Server.\n");

    while (1) {

        // recv() receives the message
        // from server and stores in buffer
        if (recv(clientSocket, buffer, 1024, 0)
            < 0) {
            printf("Error in receiving data.\n");
        }

        // Printing the message on screen
        else {
            printf("Server: %s\n", buffer);
            bzero(buffer, sizeof(buffer));
        }
    }

    return 0;
}