With the rapid development of Large Language Models (LLMs), communication mechanisms in Multi−Agent Systems (MAS) have evolved from ontology−based protocols such as KQML to LLM−driven architectures. This paper reviews the Agent−to−Agent (A2A) protocol proposed by Google and the Model Context Protocol (MCP) introduced by Anthropic, which together form the MCP×A2A protocol stack. This stack provides a unified interface for agent−level tool invocation and function sharing, forming a foundational layer for the so−called "Internet of Agents". However, the current MCP×A2A system primarily enables functional interoperability and remains insufficient for supporting deep collaboration involving multiple users and agents, especially in terms of dynamic coordination and emotional alignment. To address these limitations, we propose the Smart Synergetic Network, built on A2A/MCP, and as a human−centered architecture grounded in Human−Engaged Computing (HEC). It introduces three integrated layers—Biophysics, Intellect, and Xin—to support full−spectrum collaboration by sensing physical state, structuring task flows, and adjusting emotional dynamics. This layered system dynamically adapts collaboration rhythms and interaction styles to individual user states, enhancing agent understanding and responsiveness. By addressing issues such as mismatched pacing and insufficient empathy in human−AI coordination, the architecture facilitates more flexible, sustainable, and trust−based collaboration. Case studies in education and remote healthcare demonstrate the system's potential to shift AI applications from simple interoperability to deeply synergized interaction.