/* Socket Server that does a wait() for a child when it terminates */
/*
 * An modified example of server using TCP protocol.
 *  (UNIX NETWORK PROGRAMMING, by Richard Stevens,
 *        Prentice Hall, 1990, pp. 284-286)
 *
 * The program forks a process for each cli program.
 * It reads one message from a socket which is connected
 * with the cli program.  It prints out the message on the stderr,
 * modifies the message, and sends the message back to the cli program.
 */

#include <stdio.h>
#include <sys/types.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>

#include <unistd.h>
#include <signal.h>
#define  period 3

#include "message.h"

#define SERV_HOST_ADDR "156.12.127.18"
/* pooh's Internet address, defined in /etc/hosts */

extern int *handler(int);

main(argc, argv)
int argc;
char *argv[];
{
    int sockfd, newsockfd, clilen, pid, err,ok;
    struct sockaddr_in cli_addr, serv_addr;
    int SERV_TCP_PORT;
    char *pname;
    MES message, tmp;

    if (signal(SIGCHLD,handler)==SIG_ERR) {
	perror("Setting Up Signal Catch");
    }

    /* SERV_TCP_PORT is the port number on kiwi used by this
       server program */
    printf("Please input an integer which is larger than 1023.\n");
    scanf("%d", &SERV_TCP_PORT);
    if(SERV_TCP_PORT > 1023)
	printf("Please run the program cli now.\n");
    else
    { 	printf("Wrong input.\n"); exit(1); }
    
    pname = argv[0];

    /* create a socket which is one end of a communication channel */
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    { perror("server: cannot open stream socket"); exit(1); }

    /* initialize server address */
    bzero((char *) &serv_addr, sizeof(serv_addr)); /* reset */
    serv_addr.sin_family = AF_INET; /* address family: Internet */
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
         /* accept a connection on any Internet interface */
    serv_addr.sin_port = htons(SERV_TCP_PORT); /* specify port number */

    /* associate server address with the socket */
    if(bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr))
       < 0)
    { perror("server: cannot bind local address"); exit(2); }

    /* specify the queue size of the socket to be 5 */
    listen(sockfd, 5);

    while(1)
    {
	clilen = sizeof(cli_addr);

	/* wait for connection from the cli program.  Once connected, */
	/* newsockfd is the fd to be used with read() and write()  */
        ok=0;
        do {
	 if((newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,
			   &clilen)) < 0) {
           if (errno != EINTR)
	    { perror("server: accept error"); exit(3);  }
         }
         else ok=1;
        } while (!ok);

	if((pid = fork()) < 0)
	  { perror("server: fork"); exit(4); }
	else if(pid==0) /* child process */
	  {
	    while(1)
	      {
		if((err = read(newsockfd, &tmp, sizeof(MES))) == -1)
		  { perror("server: read"); exit(4); }
		else if (err == 0) exit(5);

		message.mtype = ntohl(tmp.mtype);
		message.number = ntohl(tmp.number);
		fprintf(stderr, "server output: %d %d\n",
			message.mtype, message.number);

		tmp.mtype = htonl(message.mtype + 1000);
		tmp.number = htonl(message.number + 1000);
	
		if(write(newsockfd, &tmp, sizeof(MES)) == -1)
		  { perror("server: write"); exit(6); }
	      }
	  }
	close(newsockfd);
        /* do nothing else for the parent process */
    }
}

int *handler(sig)
int sig;
{   int result;
    pid_t pid;
    fprintf(stderr,"Parent Server: Caught Signal %d\n",sig);
    pid=wait(&result);
    fprintf(stderr,"wait() gets pid %d with return code %d\n",pid,result);
    return(NULL);
}