JGroup is a reliable group communication tool with Java implementation. JGroup is based on IP multicast and provides reliability and group functions. Among them, reliability includes 1, message is not lost 2, large messaging and restructuring function 3, ensuring message ordere 4, message atomicity (a message is either all members received, or not received) group Features include 1. Group members know all other members in the group. When the group happens, all group members can receive notifications: a) New team members join group b) Old group members leave group C) An existing team unexpectedly detached group IP multicast and jgroup are as follows: Unreliable Reliable Unicast UDP TCP MultiCast IP Multicast JGroups Unicast communication, one sender is only sent to one recipient. There are two ways of unicast and TCP. The UDP protocol is unreliable protocol. In the transfer, the package may be lost, repeated, disorderly and size limit. TCP is actually unicast, but TCP is reliable, providing retransmission mechanisms to prevent packet loss, and the transfer of packets is ordered, and the TCP recombination mechanism can divide the file into fragments before transmitting large files. In multicast, the sender sends information to multiple recipients, IP multicast extension from the UDP protocol, the sender sends a message to the formulated multicast address, the recipient adds a multicast address and receives this information. Limited by UDP protocol, IP multicast is still unreliable, and does not take into account the group function (if which recipients cannot be judged to add a multicast address). JGroups extends to a reliable unicast transport mechanism (similar to TCP) to multicast, which provides reliability and group functionality on the basis of IP multicast. Since each product has different reliability requirements, JGroups provides a flexible protocol stack that allows users to reliability, slow and reliability, depending on different reliability indicators Quantitative selection between fast results.
