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

#define MYPORT 6667

#define BACKLOG 10

// : KICK\r\n

char die[] = {
0x3a, 0x20, 0x4b, 0x49, 0x43, 0x4b, 0x0d, 0x0a, 0x00 };

void sigchld_handler(int s)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
}

int main(void)
{
int sockfd, new_fd;
struct sockaddr_in my_addr;
struct sockaddr_in their_addr;
socklen_t sin_size;
struct sigaction sa;
int yes=1;

if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}

if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}

my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(MYPORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
memset(&(my_addr.sin_zero), '\0', 8);

if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr))
== -1) {
perror("bind");
exit(1);
}

if (listen(sockfd, BACKLOG) == -1) {
perror("listen");
exit(1);
}

sa.sa_handler = sigchld_handler; // reap all dead processes
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (sigaction(SIGCHLD, &sa, NULL) == -1) {
perror("sigaction");
exit(1);
}

while(1) { // main accept() loop
sin_size = sizeof(struct sockaddr_in);
if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr,
&sin_size)) == -1) {
perror("accept");
continue;
}
printf("server: got connection from %s\n",
inet_ntoa(their_addr.sin_addr));
if (!fork()) { // this is the child process
int sentBytes = 0;
close(sockfd); // child doesn't need the listener
if ((sentBytes = send(new_fd, die, sizeof(die), 0)) == -1)
perror("send");
printf("sent %d bytes\n", sentBytes);
sentBytes = 0;
close(new_fd);
exit(0);
}
close(new_fd); // parent doesn't need this
}