This paper describes the concept and techniques to construct a community-based cross-industrial IoT service platform by utilizing already-existing fixed and mobile facilities as wireless IoT gateways geo-distributed in a city, which will enable quick implementations of local IoT services to bring social and economical values. Our proposed concept follows the policy of "local data production for local data consumption" considering the fact that locally available but socially-valuable data can provide various kinds of IoT service without the need of any cellular phone network, or cloud/data center facility to process big data. A prototyping platform to demonstrate this concept was constructed in Tokyo, Japan by utilizing a soft-drink maker's facilities, i.e., vending machines and beverage delivery trucks, and taxi service company's facilities, i.e., taxis. The function of the platform as a data forwarding network to disseminate socially-valuable data is demonstrated, and the performance is evaluated.