This function recives packet from peer along conn within timeout miliseconds (see yw_conn_recv(3) for discussion about it). However, when packet, which is not reply is recived, it's queued, to be fetched uppon next call to yw_conn_recv(3). When reply packet is fetched, it's returned immidietly. This function can take more then timeout miliseconds to complete, when there are packets avaialble which come in less then timeout ms, but which are not of reply type.