/* 25Oct23: Network-client Beispiel + Aufgabe aus den Folien
 *
 * Keine Garantie auf Richtigkeit!  Stand unverändert aus der
 * Tafelübung, am besten nichts kopieren sondern selbst schreiben! */

#include <ctype.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

void process(FILE *rx, FILE *tx)
{
     int mode = fgetc(rx), c;

     int (*conv)(int);
     switch (mode) {
     case 'l':
	  conv = tolower;
	  break;
     case 'u':
	  conv = toupper;
	  break;
     default:
	  return;
     }

     while ((c = fgetc(rx)) != EOF) { /* FEHLER */
	  fputc(conv(c), tx);	/* FEHLER */
	  fflush(tx);
     }
}

int main(int argc, char *argv[])
{

     struct addrinfo *res, *iter;
     int err, sock, copy;

     err = getaddrinfo(argv[1], argv[2], &(struct addrinfo) {
	  .ai_socktype = SOCK_STREAM,
	  .ai_family = AF_UNSPEC,
	  .ai_flags = AI_ADDRCONFIG,
     }, &res);			     /* FEHLERBEHANDLUNG */
     (void) err;

     for (iter = res; iter != NULL; iter = iter->ai_next) {
	  sock = socket(iter->ai_family,
			    iter->ai_socktype,
			    iter->ai_protocol);
	  if (0 == connect(sock, iter->ai_addr, iter->ai_addrlen)) {
	       break;
	  }
	  close(sock);
     }
     if (iter == NULL) {
	  /* FEHLERBEHANDLUNG mit gai_strerror */
	  return EXIT_FAILURE;
     }

     FILE *rx = fdopen(sock, "r");
     copy = dup(sock);
     FILE *tx = fdopen(copy, "w");

     process(rx, tx);

     fclose(rx);
     fclose(tx);

     return 0;
}