#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>

#ifndef NO_SIGCHLD_HANDLER
#include <signal.h>
void sigchld_handler( int a )
{
  while ( waitpid( -1, NULL, WNOHANG ) > 0 );
}
#endif /* NO_SIGCHLD_HANDLER */

#define MYPORT  3490
#define BACKLOG 1

inline void doit( int connfd )
{
  char input;
  int recvd;
  while ( 1 ) 
    { 
      recvd = recv( connfd, &input, 1, 0 );
      if (  recvd == -1  )
	{
	  perror( "recv" );
	  break;
	}
      else if (  recvd == 0  )
	{
	  struct sockaddr_in name;
	  unsigned int sin_size = sizeof( struct sockaddr_in );
	  if ( getpeername( connfd, (struct sockaddr *) &name,
			    &sin_size ) == -1 )
	    {
	      perror( "getpeername" );
	      exit( 1 );
	    }
	  
	  printf( "server: closing connection  %s:%d\n",
		  inet_ntoa( name.sin_addr), 
		  ntohs( name.sin_port ) );
	  break;
	}
      if (  send(  connfd, &input, 1, 0  ) == -1  )
	{
	  perror( "send" );
	  break;
	}
    }
}

inline void forkit( int listenfd, int connfd )
{
  int pid;
  if ( ( pid = fork() ) == 0 )
    {
      close( listenfd );
      doit( connfd );
      close( connfd );
      exit( 0 );
    }
  else if ( pid == -1 )
    {
      perror( "fork" );
    }
  close( connfd );
}

int main( void )
{
    int sockfd, new_fd;
    struct sockaddr_in my_addr;
    struct sockaddr_in their_addr;
    unsigned int sin_size;
#ifndef NO_SIGCHLD_HANDLER
    void (*sigchld_bkp)(int) ;
    if ( ( sigchld_bkp = 
	   signal( SIGCHLD, sigchld_handler ) ) == SIG_ERR )
      {
	fprintf( stderr, "ERROR: could not change "\
		 "signal SIGCHLD handler!\n" );
	exit( 1 );
      }
#endif /* NO_SIGCHLD_HANDLER */
    if ( ( sockfd = socket( AF_INET, SOCK_STREAM, 0 ) ) == -1 ) 
      {
        perror( "socket" );
        exit( 1 );
      }
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons( MYPORT );
    my_addr.sin_addr.s_addr = INADDR_ANY;
    memset( &( my_addr.sin_zero ), '\0', 8 );
    if ( bind( sockfd, ( struct sockaddr * )&my_addr, 
	       sizeof( struct sockaddr ) ) == -1 ) 
      {
        perror( "bind" );
        exit( 1 );
      }
    if ( listen( sockfd, BACKLOG ) == -1 ) 
      {
	perror( "listen" );
        exit( 1 );
      }
    while( 1 ) 
      {
        sin_size = sizeof( struct sockaddr_in );
        if ( ( new_fd = accept( sockfd, 
				( struct sockaddr * )&their_addr,
				&sin_size ) ) == -1 ) {
	  perror( "accept" );
	  continue;
        }
        printf( "server: got connection from %s:%d\n",
		inet_ntoa( their_addr.sin_addr ),
		ntohs( their_addr.sin_port) );
	forkit( sockfd, new_fd );
      }
#ifndef NO_SIGCHLD_HANDLER
    signal( SIGCHLD, sigchld_bkp );
#endif /* NO_SIGCHLD_HANDLER */
    return 0;
}

/* author: Gustavo Sverzut Barbieri (http://www.gustavobarbieri.com.br) */