Lookup services enable communications over a network.
A client program can use a lookup protocol to get information on remote programs or machines and use that information to establish a communication. Programs use the DNS mapping to look up the IP address associated with a machine name and use the IP address to establish a communication. In the same way, the AuctionServlet presented in Chapter 2 uses the naming service built into the Enterprise JavaBeans TM architecture to look up and reference Enterprise Beans registered with the Enterprise JavaBeans TM server. In addition to naming services, some lookup protocols provide directory services. This attribute can be used to restrict access to a machine so only the users in the specified workgroup have access.