developers:apiv2:faq [Documentation]

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====== FAQ ======

[[developers:apiv2|◀ WebSocket API (V2)]]

=== Which endpoint should I use? ===
Develop and certify on the Simulator (''wss://wss-sim.t4login.com/v2''); use Live (''wss://wss.t4login.com/v2'') only after certification.

=== Do I need to re-subscribe after reconnecting? ===
Yes. Sessions are not resumable. After any disconnect, log in again and re-subscribe to your markets and accounts, then reconcile order state from the account snapshot.

=== Why are prices and volumes sent as strings? ===
To carry exact decimal values with no floating-point rounding, and to support fractional order volumes. Parse them into a native decimal type. See [[developers:apiv2:pricing|Prices & Data Types]].

=== Do I have to subscribe to an account before trading? ===
Yes. Orders routed into an account you have not subscribed to are rejected.

=== MBP or MBO? ===
Use **MBP** (Market by Price) for aggregated depth. Use **MBO** (Market by Order) when you need individual orders or queue position. See [[developers:apiv2:markets|Market Data]].

=== Where is the full list of every field? ===
In the ''.proto'' files — see the [[developers:apiv2:reference|Message Catalog]].

=== I'm on V1. What changes? ===
See [[developers:apiv2:migrating|Migrating from V1]].