Function nanomsg_sys::nn_close

pub unsafe extern "C" fn nn_close(socket: c_int) -> c_int

"Closes the socket s. Any buffered inbound messages that were not yet received by the application will be discarded. The library will try to deliver any outstanding outbound messages for the time specified by NN_LINGER socket option. The call will block in the meantime."

http://nanomsg.org/v0.4/nn_close.3.html