anchor.diff:  
               port = mkOption {
                 default = 8898;
  -              type = types.int;
  +              type = types.port;
                 description = "Port to listen to when serving files from cache.";
               }; # nslave.http.port
   
  
positive.code: 
        port = mkOption {
          default = 14311;
          type = types.int;
          description = "Specify port to listen on.";
        }; # qserve.port
  
  
negative.code: 
        port = mkOption {
          default = 8899;
          type = types.port;
          description = "Specify port to listen on.";
        }; # nserve.port
  
  