The client server model and software design; concurrent processing in client-server software; program interface to protocols; the TLI interface; algorithms and issues in client software design; example client software; algorithms and issues in server software design; interactive, connectionless servers (UDP); single-process concurrent servers (TCP); multiprotocol servers (TCP, UDP); multiservice servers (UDP, TCP); uniform, efficient management of server concurrency; concurrency in clients; tunnelling at the transport and application levels; application level gateways; external data representation (XDR) remote procedure call concept (RPC); distributed program generation (Rpcgen Concept); network file system concept (NFS); network file system protocol (NFS Mount); TELNET - an example client design; TELNET - an example server design; practical hints and techniques for UNIX servers. Appendices.