Opportunistic Internet of Things (IoT) extends the concept of opportunistic networking combining human users carrying mobile devices and smart things. It explores the relationships between humans and the opportunistic connection of smart objects. This paper presents a software infrastructure, named Opportunistic IoT Platform (OIoT), which helps developers to create and manage opportunistic IoT communities between smart devices. The platform enables the creation of opportunistic IoT communities that support the AllJoyn communications framework, for IoT devices and applications. Results from a preliminary evaluation of the OIoT platform indicate that this infrastructure is useful to manage and share data across opportunistic IoT communities.