# File lib/mongo/mongo_client.rb, line 177
    def parse_init(host, port, opts)
      if host.nil? && port.nil? && ENV.has_key?('MONGODB_URI')
        parser = URIParser.new(ENV['MONGODB_URI'])
        if parser.replicaset?
          raise MongoArgumentError,
            "ENV['MONGODB_URI'] implies a replica set."
        end
        opts.merge! parser.connection_options
        [parser.host, parser.port]
      else
        [host || DEFAULT_HOST, port || DEFAULT_PORT]
      end
    end