          # File lib/eventmachine.rb, line 1651
    1651:         def start_tls args={}
    1652:           priv_key, cert_chain = args.values_at(:private_key_file, :cert_chain_file)
    1653:
    1654:           [priv_key, cert_chain].each do |file|
    1655:             next if file.nil? or file.empty?
    1656:             raise FileNotFoundException,
    1657:               "Could not find #{file} for start_tls" unless File.exists? file
    1658:     end
    1659:
    1660:                 EventMachine::set_tls_parms(@signature, priv_key || '', cert_chain || '')
    1661:
    1662:                 EventMachine::start_tls @signature
    1663:         end