We agree that the Canon was established the late 300s.
That was before the Great Schism (in 1054) when West (Catholic) and East (Orthodox) were separated.
Of course we have different opinions about "who split off from whom", but that is another topic.
Both of us have Apostolic succession (i.e. we can trace the hands that ordained our clerics, and the hands that ordained their ordainers, and so on, all the way back to the Apostles who were ordained by Christ).