Research in mobile networks and pervasive computing has shown that dynamic adaptation and context-awareness are basic requirements for applications executing in such environments. Many of the works about context-awareness dynamic adaptation found in the literature use the device's context information to execute an adaptation only locally at the device. For distributed, context-aware applications composed of a group of portable devices (executing in a wireless network) sometimes it is necessary to perform a collective and coordinated adaptation at all the devices of the group, and where this adaptation depends on the global context of the group. This thesis presents Moratus, a protocol that processes the global context of a group and executes a unique adaptation of a communication service at all devices in the group in a coordinated way. This protocol also handles unplanned disconnections of group members during the adaptation process. Moratus is the central element of a middleware named SACS, which allows that such coordinated adaptation is performed transparently and without disruption for the distributed application based on this middleware.