#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <netdb.h>
extern int h_errno;

#define MAXBUF 80

void child_func(int childnum, struct in_addr servIP, int port);

void blad(char * message)
{
	fprintf(stderr, "%s\n", message);
	exit(1);
}

struct in_addr inet_addr_from_any(char * addr)
{
	struct hostent *host;
	struct in_addr in;

	in.s_addr = inet_addr(addr);

	if (in.s_addr == -1)
	{
		if ((host = gethostbyname(addr)))
		{
			in = *((struct in_addr *)(host->h_addr_list[0]));
			return in;
		} else {
			blad("nieprawidlowy adres");
		}
	}
	return in;
}

int isNumber(char * string)
{
	int i = 0;
	for (i = 0; string[i] != 0; ++i)
	{
		if (string[i] < '0' || string[i] > '9')
		{
			return 0;
		}
	}
	return 1;
}

int anyPort_to_int(char * string)
{
	FILE * potok;
        char buffer[MAXBUF];
	int readed;
	char * portStart;
	char * cp;

	if (isNumber(string))
	{
		portStart = string;
	} else {
		snprintf(buffer, sizeof(buffer), "getent services %s", string);
		potok = popen(buffer, "r");
		if (potok == NULL) blad("popen() error");
		if (feof(potok)) blad("can't find given port number");
		readed = fread(buffer, sizeof(char), sizeof(buffer), potok);
		if (ferror(potok)) blad("fread() error");
		if (readed == 0) blad("can't find given port number");
		buffer[readed - 1] = 0;

		for (cp = buffer; *cp != '/'; cp += sizeof(char))
		{
			if (*(cp - sizeof(char)) == ' ' && *cp >= '0' && *cp <= '9')
				portStart = cp;
		}
		cp = 0;
	}
	return atoi(portStart);
}

int main(int argc, char *argv[])
{
    int nchildren = 1;
    struct in_addr servIP;
    int port;
    int pid;
    int i;

    if (argc < 4) {
      fprintf(stderr, "Uzycie: %s <serwer> <port> <liczba klientow>\n",
              argv[0]);
      exit(1);
    }
    servIP = inet_addr_from_any(argv[1]);
    port = anyPort_to_int(argv[2]);
    nchildren = atoi(argv[3]);
    printf("adres IP: %s\n", inet_ntoa(servIP)); /* DEBUG */
    printf("    port: %i\n", port); /* DEBUG */
    for (i = 0; i < nchildren; i++) {
        if ((pid = fork()) == 0) {
            child_func(i + 1, servIP, port);
            exit(0);
        }
    }
    wait(NULL);
    return 0;
}

void child_func(int childnum, struct in_addr servIP, int port)
{
    int sock;
    struct sockaddr_in sAddr;
    char buffer[MAXBUF];
    

    sock = socket(PF_INET, SOCK_STREAM, 0);
    sAddr.sin_family = AF_INET;
    sAddr.sin_addr.s_addr = servIP.s_addr;
    sAddr.sin_port = htons(port);
    
    if (connect(sock, (const struct sockaddr *) &sAddr, sizeof(sAddr)) != 0) {
      perror("klient");
      return;
    }
      
    snprintf(buffer, MAXBUF, "Dane od klienta %i.", childnum);
    sleep(1);
    printf("Potomek %i wyslal %i znakow\n", childnum, 
            write(sock, buffer, strlen(buffer)));
    sleep(1);
    printf("Potomek %i otrzymal %i znakow\n", childnum, 
            read(sock, buffer, MAXBUF));
    sleep(1);
    close(sock);
}