Passing Structures into Functions

You are correct, both forms only create a 'type'. You can exemplify this by slightly changing the first form into

typedef  struct { 
    enum { READY, COMPLETE, CLOSE } state; 
    int fd; 
    int close; 
    INT8U rx_buffer; 
    INT8U *rx_rd_pos; /* position we've read up to */
    INT8U *rx_wr_pos; /* position we've written up to */
    } SSSConn;

SSSConn master , slaves ;