Each running copy of TWS has a Socket Port number used to communicate with 3rd party applications. Normally TWS is setup to listen for API connections on socket port number 7496. Leave one TWS setup with socket port 7496. Go to the other TWS and use the Configure Menu Configure → API → Socket Port and enter some other port number, e.g 7497. In Investor/RT, use the IB Menu; IB → Setup and set the Port setting to the socket port number of the TWS to which you wish to connect. Then Start Feed and Investor/RT will connect to the TWS that has the specified port number.
