Abstract: A client-server system includes a new front end server which interposes itself between a prior (back end) server and its clients using an interposed dynamically-loaded library linked to the back end. The interposed library and front end can provide enhanced services without requiring reconfiguration of either the back end server or its clients. The front end can accept network connections on the same port as the back end server is programmed to. The interposed library intercepts standard network system calls by the back end and emulates their behavior by communicating with the front end. The front end can send file descriptors of either direct connections with clients, or of pipes for relaying requests and response from and to clients through the front end, to the interposed library for return to calls by the back end to accept connections.