val t : send_ack:Sequence.t Lwt_mvar.t -> last:Sequence.t -> tval receive : t -> Sequence.t -> unit Lwt.tval pushack : t -> Sequence.t -> unit Lwt.tval transmit : t -> Sequence.t -> unit Lwt.tAck.Immediateval t : send_ack:Sequence.t Lwt_mvar.t -> last:Sequence.t -> tval receive : t -> Sequence.t -> unit Lwt.tval pushack : t -> Sequence.t -> unit Lwt.tval transmit : t -> Sequence.t -> unit Lwt.t