It is posted at the following location on System Documents Site.
[System Documents Site]
System Documents > arrowhead/ToSTNeT/FLEX > Connection Specifications/Guidelines Related
URL:
https://faqsd.jpx.co.jp/category/show/621?site_domain=en_system_documents- [arrowhead4.0]FLEXConnectionSpecification_DS.xx.x
- [arrowhead4.0]FLEX_MarketbyOrderSpecifications_ver.x.x