How can I get all the stocks of each accounts in Interactive Broker IB API?

Question

I have a Master Account which manages multiple accounts. How can I get the portfolio of each accounts? I've been trying the self.reqPositions() but it returns just the accounts with recent trades.

for example I have 3 accounts and the I have transactions on just 1 account so the 2 other accounts do not have any transactions on that day but I want to get their current portfolio:

U1234567
AAPL - 200 stcks
MSFT - 200 stcks

U7654321
AAPL - 300 stcks
FB - 500 stcks 

Follow up question would be, how can I place an order for each account not on Master Account? Thank you for answering.