On https://github.com/sdroege/rtsp-server/blob/master/src/listener/message_socket.rs, it does
use crate::body::Body;
I could only find information about external crates: https://doc.rust-lang.org/reference/items/extern-crates.html
What does use crate:: mean?
It refers to to the crate currently being compiled. So in this example, it is resolved as rtsp_server::body::Body. The body::Body part is refering to the Body item in the body module.
crateis also used to represent the absolute path of a module, wherecraterefers to the root of the current crate. For instance,crate::foo::barrefers to the namebarinside the modulefoo, from anywhere else in the same crate.