#include <stdio.h>
#include <stdlib.h> 
#include <errno.h> 
#include "gis.h" 

int main (int argc, char *argv[]) 
{ 
  int listenfd, rwfd; 
  char *path; 
  pid_t pid; 
  struct sockaddr_un addr = {0};
  /* Path is built using server's name */ 
  // path: F-des
  if (NULL == (path = G_sock_get_fname (argv[0]))) 
    exit (EXIT_FAILURE); 

  /* Make sure another instance isn't running */ 
  if (G_sock_exists (path)) 
  { 
    if ((listenfd = G_sock_connect (path)) != -1) 
    { 
      close (listenfd);
      exit (EXIT_FAILURE); 
    } 
    remove (path); 
  } 
  /* Bind the socket */ 
  // listenfd: F-des, path: F-des
  if ((listenfd = G_sock_bind (path)) < 0) 
    exit (EXIT_FAILURE); 

  /* Begin listening on the socket */ 
  // 1: int queue length, should never be = 0
  if (G_sock_listen (listenfd, 1) != 0) 
    exit (EXIT_FAILURE); 

  /* Loop forever waiting for connections */ 
  for (;;) 
  { 
    if ((rwfd = G_sock_accept (listenfd)) < 0) { 
      if (errno == EINTR) 
	continue; 
    } 
    else 
      exit (EXIT_FAILURE); 

    /* Fork connection */ 
    // parent process: listen to socket
    // child process: process request
    // pid: pid of new child process
    if ((pid = fork()) == 0) { 
      char c; 
      /* child closes listenfd */ 
      close (listenfd); 
      // rwfd: F-des, c: Zeichenvektor,aus dem Zeichen gelesen werden sollen
      // 1: Anz zu lesende bytes
      while (read (rwfd, &c, 1) > 0) 
	write (rwfd, &c, 1); // schreibt 1 char von c in rwfd
      close (rwfd); 
      return 0; 
    } 
    else if (pid > 0) { 
      /* parent closes rwfd 
       * a well behaved server would limit 
       * the number of forks. */ 
      close (rwfd); 
    } 
    else 
      exit (EXIT_FAILURE); 
  } 
  G_free (path); 
  return 0; 
}