smux multiplexes multiple TCP connections?

[caleb-letsgo]

As I understand, smux uses a single TCP connection to simulate the effect of multiple virtual TCP connections. But kcptun says smux is designed to host multiple TCP links on the same connection.
If you have multiple TCP connections, you have the same source and destination addresses, but different ports. So the user needs to maintain which TCP connection a stream represents. Do I understand that correctly?
Can you recommend git projects that use smux?