#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCK_NAME "./socket"

int main()
{
  int i;
  int fd1, fd2;
  struct sockaddr_un saddr;
  struct sockaddr_un caddr;

  int len;
  int ret;
  char buf[1024];

  if ( ( fd1 = socket( AF_UNIX, SOCK_STREAM, 0 ) ) < 0 ) {
    perror( "socket" );
    exit( 1 );
  }

  memset( (char *)&saddr, 0, sizeof( saddr ) );
  saddr.sun_family = AF_UNIX;
  strcpy( saddr.sun_path, SOCK_NAME );

  unlink( SOCK_NAME );
  if ( bind( fd1, ( struct sockaddr * )&saddr, ( socklen_t )sizeof( saddr ) ) < 0 ) {
    perror( "bind" );
    exit( 1 );
  }

  if ( listen( fd1, 5 ) < 0 ) {
    perror( "listen" );
    exit( 1 );
  }

  while( 1 ) {
    len = sizeof( caddr );
    if ( ( fd2 = accept( fd1, ( struct sockaddr * )&caddr, ( socklen_t * ) &len ) ) < 0 ) {
      perror( "accept" );
      exit( 1 );
    }
    fprintf( stderr, "Connection established: socket %d used.\n", fd2 );

    while( ( ret = read( fd2, buf, 1024 ) ) > 0 ) {
      fprintf( stderr, "read: %s\n", buf );
      for ( i=0; i<ret; i++ )
	if ( islower( buf[i] ) ){
	  buf[i] = toupper( buf[i] );
    }
	else if(isupper(buf[i])){
	  buf[i] = tolower(buf[i]);
	}
      fprintf( stderr, "write: %s\n", buf );
      write( fd2, buf, 1024 );
      fsync( fd2 );
    }

    close( fd2 );
  }

  close( fd1 );

  return 0;
}