This extended abstract presents a coupling method for the Fluid-Structure Interaction (FSI) problem, which aim is to be conservative and to use classical spaciotemporal discretization methods on each sub-domains; fluid and structure. In this way, the coupling is based on a monolithic formulation and solved by a co-simulation algorithm. The structural sub-domain is spatially discretized by finite elements method and temporally discretized by Newmark implicit scheme. While the fluid sub-domain is discretized by finite volumes method and Runge-Kutta order 2 explicit scheme. The long-term objective is to couple two existing commercial softwares. The proposed method is validated using the one-dimension piston test case