In multiple datacenters-based cloud environments, virtual machines migrates across nodes located in the same or different datacenter to provide users with efficient resource provisioning services. Especially, migration between nodes located in different datacenter usually works on a wide area network. However, it takes a longer time than a local area network-based migration to transfer virtual devices' state. In addition, it might change IP address of the migrated virtual machine on the target node. Therefore, in the wide area network-based migration, it is necessary to carefully consider migration transparency. This paper proposes a virtual machine location management and a reliable message delivery protocol for wide area network-based multiple datacenters cloud environments to guarantee message delivery to the migrated virtual machine. In addition, this paper also presents a smart-copy migration method for virtual machines to adaptively migrate according to network status.