In recent years, there has been an increasing interest in opinion dynamics in social networks. The present paper proposes an attempt to develop a computational framework for such dynamics in continuous time with an additive noise representing self-beliefs. We derive a partial differential equation for the distribution of opinions differences. The main point is that there is a calculus based on Mellin transforms that allows one to solve this type of equations in closed form. The main new result of this approach is a closed form solution for the bounded confidence model within this stochastic continuous time framework. This is done here in the simplest possible cases (small number of agents, present of stubborn agents, one dimensional opinions).