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

#define BUF_SIZE 512

int main(int argc, char *argv[])
{
    fd_set all_fds;                 /* Master set where we keep all file descriptors */
    fd_set read_fds;                /* This is a temporary set we will use with select() */
    int listen_fd;                  /* File descriptor for listening */
    int client_fd;                  /* File descriptor for clients */
    struct sockaddr_in addr;        /* Struct that holds server address */
    struct sockaddr_in cli_addr;    /* Struct that holds client address */
    socklen_t cli_addrlen = sizeof(cli_addr);
    ssize_t nbytes;
    int fd, i;
    char data[BUF_SIZE];

    memset(data, '\0', BUF_SIZE);

    /* empty the file descriptor sets */
    FD_ZERO(&all_fds);
    FD_ZERO(&read_fds);

    /* initialize the struct with the server address */
    addr.sin_family      = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port        = htons(12345);
    memset(addr.sin_zero, '\0', sizeof(addr.sin_zero));

    /* Create the listening socket */
    listen_fd = socket(PF_INET, SOCK_STREAM, 0);

    /* Assign server address to the socket */
    bind(listen_fd, (struct sockaddr *)&addr, sizeof(addr));

    /* Start listening for connections */
    listen(listen_fd, 10);

    /* Add listen socket fd to the master set */
    FD_SET(listen_fd, &all_fds);

    for(;;)
    {
        read_fds = all_fds;
        /* select blocks until one of our sockets has data to read */
        select(FD_SETSIZE, &read_fds, NULL, NULL, NULL);

        for (fd = 0; fd < FD_SETSIZE; fd++)
        {
            /* is the file descriptor ready for reading? */
            if (FD_ISSET(fd, &read_fds))
            {
                /* if it is the listening fd then we got a new connection */
                if (fd == listen_fd)
                {
                    /* accept the connection */
                    client_fd = accept(listen_fd, (struct sockaddr *)&cli_addr, &cli_addrlen);

                    /* add fd to the master fd set */
                    FD_SET(client_fd, &all_fds);
                }
                else
                {
                    /* else someone is trying to send data */
                    nbytes = read(fd, data, BUF_SIZE-1);

                    switch(nbytes)
                    {
                        case -1:
                            /* an error occured */
                            perror("read");
                            exit(1);
                        case  0:
                            /* client disconnected */
                            fprintf(stderr, "server: socket %d closed connection\n", fd);

                            /* remove fd from the master fd set */
                            FD_CLR(fd, &all_fds);
                            break;
                        default:
                            data[nbytes - 1] = '\0';
                            fprintf(stderr, "socket %d: %s\n", client_fd, data);

                            for (i = 0; i < FD_SETSIZE; i++)
                            {
                                /* send the message to everyone except from
                                 * the sender and the server 
                                 */
                                if (FD_ISSET(i, &all_fds) && i != fd && i != listen_fd)
                                    write(i, data, nbytes);
                            }
                    }
                }
            }
        }
    }
    return 0;
}