  To characterize the Neumann problem for nonlinear Fokker-Planck equations, we
investigate distribution dependent reflecting SDEs (DDRSDEs) in a domain. We
first prove the well-posedness and establish functional inequalities for
reflecting SDEs with singular drifts, then extend these results to DDRSDEs with
singular or monotone coefficients, for which a general criterion deducing the
well-posedness of DDRSDEs from that of reflecting SDEs is established.
