/*
 * An modified example of server using UDP protocol.
 *  (UNIX NETWORK PROGRAMMING, by Richard Stevens,
 *        Prentice Hall, 1990, pp. 284-286)
 *
 * It reads one message from a datagram socket sent from the cli program.  
 * It prints out each message received on the stderr
 * and sends the message back to the cli program using
 * the port number from the inward socket internet address record.
 */

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

/*#define SERV_HOST_ADDR "130.108.2.22"
 gamma's Internet address, defined in /etc/hosts */

// #define SERV_HOST_ADDR "156.12.23.5"
#define SERV_HOST_ADDR "156.12.1.120"
/* pooh's Internet address, defined in /etc/hosts */


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

    /* SERV_UDP_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_UDP_PORT);
    if(SERV_UDP_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_DGRAM, 0)) < 0)
    { perror("server: cannot open datagram 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_UDP_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); }


    while(1)
    {
		clilen=sizeof(cli_addr);
		err=recvfrom(sockfd, &tmp, sizeof(MES),0,(struct sockaddr *)&cli_addr, &clilen);
		if(err < 0)
		  { 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);

		if(sendto(sockfd,&tmp,sizeof(MES),0,	
			(struct sockaddr *)&cli_addr, clilen)==-1)
		  { perror("server: write"); exit(6); }
    }
}