/* tcp.slave.fork.c SJ */
/* gcc -Wall -o tcp.slave tcp.slave.c -lnsl -lsocket -lresolv
*/

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

void sendall(int sock, char *buf);

/* signal handler to wait all child processes */
void sigchld_handler(int s)
{
  while(wait(NULL) > 0);
}

int main(int argc, char **argv)
{
  int j;
  int numbytes, count, pid;

  char buf[1000];
  char mesg2[100];
  char hname[100];

  struct sockaddr_in remote_addr, my_addr;
  int sock, newsock;
  int sin_size;
  char yes='1';

  struct sigaction sa;
  
  if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
	  perror("socket");
	  exit(1);
  }

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

  if (gethostname(hname, 99) == -1) {
      perror("gethostname");
      strcpy(hname, "???");
  }

  my_addr.sin_family = AF_INET;    // host byte order
  my_addr.sin_port = htons(atoi(argv[1]));  // short, network byte order
  my_addr.sin_addr.s_addr = INADDR_ANY;	// automatically fill with my IP
  memset(&(my_addr.sin_zero), '\0', 8);  // zero the rest of the struct

  /* bind to the port */
  if (bind(sock, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {                perror("bind");
	  exit(1);
  }

  /* open port for connections */
  if (listen(sock, 5) == -1) {
	  perror("listen");
	  exit(1);
  }

  /* register signal handler which waits (ackknowledges) all childs */
  sa.sa_handler = sigchld_handler;
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = SA_RESTART;
  if (sigaction(SIGCHLD, &sa, NULL) == -1) {
	  perror("sigaction");
	  exit(1);
  }
  
  /* serve forever */
  while(1) {
	  sin_size = sizeof(struct sockaddr_in);

	  /* accept new connection */
	  if ((newsock = accept(sock, (struct sockaddr *)&remote_addr, &sin_size)) == -1) {
		  perror("accept");
		  continue;
	  }

	  printf("got connection from %s\n",inet_ntoa(remote_addr.sin_addr));

	  /* create child process to handle the new connection */
	  pid = fork();

	  if (!pid) {
		  /* child process, handle one request */
		  numbytes = recv(newsock, buf, 999, 0);
		  if (numbytes == -1) {
			  perror("recv");
			  close(newsock);
			  exit(1);
		  }
		  buf[numbytes] = '\0';   /* terminate string */

		  count = atoi(buf);              /* convert to int */

		  /* print */
		  puts(buf);

		  /* send message */
		  sprintf(mesg2, "Hello from %s(pid=%d)\n", hname, getpid());

		  for (j = 0; j < count; j++) {
			  sendall(newsock, mesg2);
		  }

		  /* close and exit */
		  close(newsock);
		  exit(0);
	  }

	  /* parent just closes newsock */
	  close(newsock);
  }

  close(sock);

  exit(0);

}


void sendall(int sock, char *buf)
{
  int len, bs;
  len = strlen(buf);
  while (len > 0) {
	  bs = send(sock, buf, len, 0);
	  if (bs == -1) {
		  perror("send");
		  return;
	  } else if (bs == 0) {
		  printf("Connection closed prematurely\n");
		  return;
	  }

	  len -= bs;
  }
} /* sendall() */