Ways to communicate
Sockets and ports are the key to both client-to-server communication and server-to-server communication. A socket is a TCP/IP connection between two ports. The command processor part of each pdserver listens for client requests on a unique port. The client or submission daemon uses a special command line protocol or an internal object-oriented API (OOAPI) protocol used by InfoPrint Manager non-command line clients. The next numbered port (client-to-server port + 1) is used by the command processor to send events to the client.
Each pdserver also listens for server-to-server requests on third unique port. These server-to-server requests use an internal platform-independent protocol that only InfoPrint Manager servers understand. This protocol not only lets InfoPrint Manager servers communicate with each other on the same or different machines, but also on the same or different platforms: AIX, Linux, and Windows.