Data communications may be carried out in a distributed computing environment that includes a plurality of computers coupled for data communications through communications adapters and an active messaging interface (‘AMI’). In such an environment, data communications may include: issuing, by a sender to a receiver, an eager SEND data communications instruction to transfer SEND data, the instruction including information describing a location and size of a send buffer in which the SEND data is stored; transmitting, by the sender to the receiver, the SEND data as eager data packets; issuing, by the receiver to the sender in dependence upon data flow conditions, a STOP instruction, the STOP instruction including an order to stop transmitting the eager data packets; and transferring the SEND data by the receiver from the sender's data location to a receive buffer by remote direct memory access (“RDMA”).