anchor.diff:  # START SQUID
   #
   ENV PORT_SQUID 13128
  -EXPOSE $PORT_SQUID/tcp
  +EXPOSE ${PORT_SQUID}/tcp
   
   RUN apt-get update -qq && apt-get install -qqy \
         apache2-utils \
  
positive.code: # START SHADOWSOCKS
  #
  
  # do not use the standard port
  ENV PORT_SHADOWSOCKS 18388
  EXPOSE $PORT_SHADOWSOCKS/tcp $PORT_SHADOWSOCKS/udp
  
  ENV SHADOWSOCKS_ENCRYPT_METHOD aes-256-cfb
  
  
negative.code: # START PPTP
  #
  
  EXPOSE 1723/tcp # PPTP Port must be standard(should not change?)
  
  # https://groups.google.com/forum/#!topic/docker-user/dC6aIr4R1hY
  #
  # inspired by https://github.com/vimagick/dockerfiles/tree/master/pptpd
  