Why rtp socket in alloc_ports_one_family() in rtsp-stream.c need bind first?

Hello, expert,

In the alloc_ports_one_family() function, I understand why RTCP needs to bind to a specific IP address and port for the client to send data.

However, since RTP sockets are sent to the client, why do they also need to be bound to a specific IP address and port?

Thank you.