training_repo/select/server_tcp_select.c

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

#define PORT 5000
#define MAX_CLIENTS 10
#define BUFFER_SIZE 256
void error(const char *msg) {
        perror(msg);
            exit(1);
}
void main()
{
    int server_fd;
    int client_fd[MAX_CLIENTS] = {0}; // Array to store client socket descriptors
    struct sockaddr_in server, client;
    fd_set readfds, copyfds;
    int max_fd, new_socket, activity, i, valread, sd;
    socklen_t addr_len = sizeof(client);
    char buffer[BUFFER_SIZE];
    // Create a TCP socket
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0)
        {
            error("Error opening socket.");
        }
     // Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(PORT);
    // Allow reuse of addresses
    int opt = 1;
    setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    // Bind the socket to the port
    if (bind(server_fd, (struct sockaddr *)&server, sizeof(server)) < 0)
    {
        error("Binding failed");
    }
    // Listen for incoming connections
    if (listen(server_fd, 5) < 0)
    {
        error("Listening failed");
    }
    printf("Listening on port %d...\n", PORT);
    while(1)
    {
        FD_ZERO(&readfds);
        FD_SET(server_fd, &readfds);
        max_fd = server_fd;
        // Add child sockets to the set
        for (i = 0; i < MAX_CLIENTS; i++)
        {
            sd = client_fd[i];
            if (sd > 0)
            {
                FD_SET(sd, &readfds);
            }
            if (sd > max_fd)
            {
                max_fd = sd;
            }
        }
         // Wait for an activity on one of the sockets
        activity = select(max_fd + 1, &readfds, NULL, NULL, NULL);
        if (activity < 0)
        {
            error("Select error");
        }
        // If something happened on the server socket, then it's an incoming connection
         if (FD_ISSET(server_fd, &readfds))
        {
            new_socket = accept(server_fd, (struct sockaddr *)&client, &addr_len);
            if (new_socket < 0)
            {
                error("Accept error");
            }
            printf("New connection from %s on socket %d\n", inet_ntoa(client.sin_addr), new_socket);
            // Add new socket to array of sockets
            for (i = 0; i < MAX_CLIENTS; i++)
            {
                if (client_fd[i] == 0)
                {
                    client_fd[i] = new_socket;
                    break;
                }
            }
        }
          // Check all clients for incoming messages
          for (i = 0; i < MAX_CLIENTS; i++)
          {
                sd = client_fd[i];
                if (FD_ISSET(sd, &readfds))
                {
                // Check if it was for closing, and also read the incoming message
                valread = read(sd, buffer, sizeof(buffer));
                if (valread > 0)
                {
                    buffer[valread] = '\0'; // Null-terminate the received string
                    printf("Message from client: %s\n", buffer);
                    // Broadcast the message to all other clients
                    for (int j = 0; j < MAX_CLIENTS; j++)
                    {
                        if (client_fd[j] != 0 && client_fd[j] != sd)
                        {
                            send(client_fd[j], buffer, strlen(buffer), 0);
                        }
                    }
                }
                }
            }
        }
    close(server_fd);
   // return 0;
    }