int vconn_connect(struct vconn *);
int vconn_recv(struct vconn *, struct ofpbuf **);
int vconn_send(struct vconn *, struct ofpbuf *);
+int vconn_recv_xid(struct vconn *, uint32_t xid, struct ofpbuf **);
int vconn_transact(struct vconn *, struct ofpbuf *, struct ofpbuf **);
int vconn_open_block(const char *name, int min_version, struct vconn **);