int fd, max_fd, tmp_fd;
int fd_array[FD_NUM];
int i, rc;
buffer buf[BUF_SIZE];
fd_set read_fd, all_fd;
struct sockaddr_in local;

local.sin_family = AF_INET;
local.sin_addr.s_addr = htonl(INADDR_ANY);
local.sin_port  = htons(PORT);

if((fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
        //error
}

if(bind(fd, (struct sockaddr*)&local, sizeof(local)) == -1)
{
        //error
}

if(listen(fd, MAX_CONNECTION) == -1)
{
        //error
}

memset(fd_array, -1, FD_NUM);
fd_array[0] = fd;

FD_ZERO(&all_fd);
FD_SET(fd, &all_fd);
max_fd = fd;

while(1)
{
        read_fd = all_fd;
        if(select(max_fd + 1, &read_fd, NULL, NULL, NULL) == -1)
        {
                continue;
        }
 
        if(FD_ISSET(fd, &readfd))
        {
                if((tmp_fd = accept(fd, NULL, NULL)) == -1)
                {
                        continue;
                }
                else
                {
                        for(i = 0; i < FD_NUM; i++)
                        {
                                if(fd_array[i] == -1)
                                {
                                        fd_array[i] = tmp_fd;
                                }
                        }
   
                        FD_SET(tmp_fd, &allfd);
                        if(tmp_fd > max_fd)
                        {
                                max_fd = tmp_fd;
                        }
                }
                continue;
        }
 
        for(i = 0; i < FD_NUM; i++)
        {
                if(FD_ISSET(fd_array[i]), &read_fd)
                {
                        rc = recv(fd_array[i], buf, BUF_SIZE, 0);
                        if(rc <= 0)
                        {
                                //error
                        }
                        else
                        {
                                buf[rc] = '\0';
                                //your operation
                        }
                        break;
                }
        }
}