Its low latency, high bandwidth, widespread support and cost-effective silicon have made PCI Express ubiquitous. It can however, be used for more than merely communicating between a host and a peripheral: it has many advantages as a peer-to-peer communications technology. Enabling this, however, demands an understanding of how PCI Express works. This paper outlines the complexities that need to be understood and overcome – and describes a Abaco Systems software product that delivers a solution that masks those complexities from developers.