**Discrete harmonic functions in the quadrant**

In this talk we shall be interested in discrete harmonic functions in cones (in particular, in the quarter plane). The generating function of these harmonic functions satisfies a functional equation (closed to a well-known functional equation that appears in the context of enumeration of confined walks in combinatorics). We shall show the link between these harmonic functions and a one-parameter family of conformal mappings. One of the motivations to that study is to condition (in the sense of Doob) random walks never to leave cones.