# Sequence Diagram

### Connectivity and Logon <a href="#connectivity-and-logon" id="connectivity-and-logon"></a>

The API client must establish a FIX session by sending a `Logon (35=A)` message. NDAX will act as an acceptor for all FIX sessions.

<figure><img src="https://451520418-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTHZFjRSbgV63RAq6J4e5%2Fuploads%2F161kAjbcD3Okg44xiJHI%2Ffix-logon.png?alt=media&#x26;token=fab2dee0-e72d-4d12-902c-ac1683cbc167" alt=""><figcaption><p>National Digital Asset Exchange's FIX Logon Message Flow</p></figcaption></figure>