Pushpin is a reverse proxy server written in C++ that makes it easy to implement WebSocket, HTTP streaming, and HTTP long-polling services. The project is unique among realtime push solutions in that it is designed to address the needs of API creators. Pushpin is transparent to clients and integrates easily into an API stack. To assist with integration, there are libraries for many backend languages and frameworks. Pushpin has no libraries on the client side because it is transparent to clients.