1. A system comprising: a server that operates in a communication network in which communication sessions are established between communications devices, the server configured to: during a communication session of a connectionless protocol, simultaneously transmit packets of voice data via the communications network from a sender communications device to a recipient communications device and buffering the packets of the voice data at the server such that the buffered packets can be resent upon receipt of an appropriate request; receive a request for missing packets from the recipient communications device, the request having been sent from the recipient communications device in response to the recipient communications device determining that at least some of the packets are missing and receiving input from a recipient requesting the voice data to be replayed at the recipient communications device; and in response to the request for the missing packets, sending the missing packets to the recipient communications device, such that the missing packets are then able to be combined with the previously transmitted packets to enable the recipient communications device to replay the voice data, which subsequently includes the missing packets, until the voice data associated with the missing packets catches up to voice data being received at the recipient communications device in real time, whereupon the recipient communications device can then resume playing the voice data being received at the recipient communications device.