Vehicular ad hoc networks (VANETs) provide an effective technology for vehicles communicating while on the road. Vehicles are organized in an ad hoc networks offering support for both safety-critical messaging, multi-hop entertainment applications, and connection to internet services through Road Side Units (RSUs). Sharing data between connected vehicles can help commuting people exchange travel information, and allows content delivery and entertainment applications using Peer-to-Peer (P2P) techniques. Despite the widely documented benefits of P2P techniques, there are a number of challenges faced when deployed in such a highly dynamic environments as VANETs. Such difficulties include the broadcast storm problem, network partition, and the temporal network fragmentation to name few. These issues are principally due to the high mobility of vehicles and thus to the constantly changing topology of the network. In this paper, we present a survey of the existing P2P approaches in the context of VANETs including a comprehensive survey of the various problems related to data sharing in VANET using P2P techniques, along with their proposed solutions from the perspective of data access, information lookup, routing, and message management. In this study, we provide a classification of the studied approaches in terms of network overlays, information structures, and network coding. To differentiate between the discussed approaches, we include a comparative study based on the crucial parameters and identify and discuss the open research challenges in P2P techniques. To the best of our knowledge, this survey constitutes the first attempt at a comprehensive analysis of P2P approaches in VANETs, which describes more appropriately the state-of-art of this specific topic of research.

车载自组织网络 (VANET) 为车辆在路上的通信提供了一种有效的技术。车辆组织在一个自组织网络中，为安全关键消息传递、多跳娱乐应用程序以及通过路边单元 (RSU) 连接到互联网服务提供支持。在联网车辆之间共享数据可以帮助通勤人员交换旅行信息，并允许使用点对点 (P2P) 技术的内容交付和娱乐应用程序。尽管 P2P 技术具有广泛记录的好处，但在 VANET 等高度动态的环境中部署时仍面临许多挑战。这些困难包括广播风暴问题、网络分区和时间网络碎片等。这些问题主要是由于车辆的高机动性以及网络拓扑结构的不断变化。在本文中，我们对 VANET 中现有的 P2P 方法进行了调查，包括对使用 P2P 技术的 VANET 中与数据共享相关的各种问题的全面调查，以及从数据访问、信息查找的角度提出的解决方案、路由和消息管理。在这项研究中，我们根据网络覆盖、信息结构和网络编码对所研究的方法进行了分类。为了区分所讨论的方法，我们包括基于关键参数的比较研究，并确定和讨论 P2P 技术中的开放研究挑战。据我们所知，