• Pure: build a subscribe message — { action, symbol, exchange, mode }, where mode is the numeric OpenAlgo data mode. Depth subscriptions may request a book depth (broker-dependent: 5/20/30/50).

    The wire key the proxy reads is depth; 1.x sent depth_level, which the proxy never read, so every request above the default was silently served at five levels. Both keys go out: depth for the proxy, depth_level for any consumer that learned the old name from this library.

    Parameters

    • mode: WsMode
    • symbol: string
    • exchange: string
    • OptionaldepthLevel: number

    Returns string