The netbuf_close function deallocates a network buffer
and closes its associated files. Use this function when you need to deallocate
the network buffer and close the socket.
You should never close the netbuf parameter in a session structure.
void netbuf_close(netbuf *buf);
netbuf *buf is the buffer to close.
netbuf_buf2sd, netbuf_getc, netbuf_grab, netbuf_open, netbuf_getbytes