  This is the second in our series of papers concerning some reversed
Hardy--Littlewood--Sobolev inequalities. In the present work, we establish the
following sharp reversed Hardy--Littlewood--Sobolev inequality on the half
space $\mathbb R_+^n$ \[ \int_{\mathbb R_+^n} \int_{\partial \mathbb R_+^n}
f(x) |x-y|^\lambda g(y) dx dy \geqslant \mathscr C_{n,p,r} \|f\|_{L^p(\partial
\mathbb R_+^n)} \, \|g\|_{L^r(\mathbb R_+^n)} \] for any nonnegative functions
$f\in L^p(\partial \mathbb R_+^n)$, $g\in L^r(\mathbb R_+^n)$, and $p,r\in
(0,1)$, $\lambda > 0$ such that $(1-1/n)1/p + 1/r -(\lambda-1) /n =2$. Some
estimates for $\mathscr C_{n,p,r}$ as well as the existence of extrema
functions for this inequality are also considered. New ideas are also
introduced in this paper.
