Live Trading

In live trading, LEAN populates the Portfolioportfolio object with your account holdings and the Transactionstransactions object with your open positions. If you don't manually subscribe to the assets in your account, LEAN subscribes to them with the lowest resolution of the subscriptions in your algorithm. For example, say you hold AAPL shares in your account and create the following subscriptions in your algorithm:

AddEquity("SPY", Resolution.Hour);
AddEquity("MSFT", Resolution.Second);

self.add_equity("SPY", Resolution.HOUR)
self.add_equity("MSFT", Resolution.SECOND)

In this case, LEAN subscribes to second-resolution data for AAPL since the lowest resolution in your algorithm is Resolution.SecondResolution.SECOND.

You can deposit and withdraw cash from your brokerage account while you run an algorithm that's connected to the account. We sync the algorithm's cash holdings with the cash holdings in your brokerage account every day at 7:45 AM Eastern Time (ET).

We notify your algorithm when your brokerage connection disconnects and reconnects.

Lost Connections

If the brokerage connection breaks, we notify your algorithm through the OnBrokerageDisconnecton_brokerage_disconnect event handler.

public override void OnBrokerageDisconnect() 
{
    Debug("Brokerage connection lost");
}

def on_brokerage_disconnect(self) -> None:
    self.debug("Brokerage connection lost")

Restored Connections

When the brokerage connection restores after it disconnects, we notify your algorithm through the OnBrokerageReconnecton_brokerage_reconnect event handler.

public override void OnBrokerageReconnect() 
{
    Debug("Brokerage connection restored");
}

def on_brokerage_reconnect(self) -> None:
    self.debug("Brokerage connection restored")

When LEAN reconnects with your brokerage, it synchronizes the state of your live orders. For example, say the brokerage fills your limit order during the period of disconnection. When the connection restores, LEAN updates the state of your portfolio and orders to reflect the filled order, but you won't receive an order event.

Example Algorithm

For a full example algorithm that implements the OnBrokerageDisconnecton_brokerage_disconnect and OnBrokerageReconnecton_brokerage_reconnect methods, see the BrokerageActivityEventHandlingAlgorithmBrokerageActivityEventHandlingAlgorithm in the LEAN GitHub repository.

When your brokerage sends you a message, we notify your algorithm through the OnBrokerageMessageon_brokerage_message event handler.

public override void OnBrokerageMessage(BrokerageMessageEvent messageEvent) 
{
    Debug(f"Brokerage message received: {messageEvent.Message}");
}

def on_brokerage_message(self, message_event: BrokerageMessageEvent) -> None:
    self.debug(f"Brokerage message received: {message_event.message}")

BrokerageMessageEvent objects have the following attributes:

For a full example algorithm that implements the OnBrokerageMessageon_brokerage_message method, see the BrokerageActivityEventHandlingAlgorithmBrokerageActivityEventHandlingAlgorithm in the LEAN GitHub repository.

To handle brokerage messages outside of your algorithm class, create and set a BrokerageMessageHandler. For a more information example, see the Reality Modeling > Brokerage Message Handler.

Brokerage features and limitations are realistically modelled with Brokerage Models. These reality models set the supported order and asset types for the brokerage. To learn how to set your specific brokerage, see Supported Models.