class Net::POP3

def do_start(account, password) # :nodoc:
  begin
    s = Socket.tcp @address, port, nil, nil, connect_timeout: @open_timeout
  rescue Errno::ETIMEDOUT #raise Net:OpenTimeout instead for compatibility with previous versions
    raise Net::OpenTimeout, "Timeout to open TCP connection to "\
        "#{@address}:#{port} (exceeds #{@open_timeout} seconds)"
  end
  if use_ssl?
    raise 'openssl library not installed' unless defined?(OpenSSL)
    context = OpenSSL::SSL::SSLContext.new
    context.set_params(@ssl_params)
    s = OpenSSL::SSL::SSLSocket.new(s, context)
    s.hostname = @address
    s.sync_close = true
    ssl_socket_connect(s, @open_timeout)
    if context.verify_mode != OpenSSL::SSL::VERIFY_NONE
      s.post_connection_check(@address)
    end
  end
  @socket = InternetMessageIO.new(s,
                                  read_timeout: @read_timeout,
                                  debug_output: @debug_output)
  logging "POP session started: #{@address}:#{@port} (#{@apop ? 'APOP' : 'POP'})"
  on_connect
  @command = POP3Command.new(@socket)
  if apop?
    @command.apop account, password
  else
    @command.auth account, password
  end
  @started = true
ensure
  # Authentication failed, clean up connection.
  unless @started
    s.close if s
    @socket = nil
    @command = nil
  end
end