A downhole modular tool includes a first module, a second module, a third module, and one or more connectors for connecting the first, second, and third modules. Each module includes a drill collar, a drilling fluid passageway, a first fluid passageway, and a second fluid passageway. The one or more connectors connect any one of the first, second, and third modules, to another of the first, second, and third modules to transfer the drilling fluid, the first fluid, and the second fluid between the connected modules.