OSF DCE Administration Guide--Core Components

DCE Application Administration
In a DCE environment, clients and their servers frequently reside on different hosts in a
network, so clients need a way to find servers.
Clients need three pieces of information to communicate with a server:
• The host name (or network address) of the host where the server is running
• The name of the network transport the server is using
• The communication port (endpoint) the server is using for client communications
Of course, an application programmer could simply hardcode a server’s location
information (also called binding information) into the client side of the application where
it is immediately available for use. However, this approach requires that a programmer
have advance knowledge of precise network details such as host names and available
port numbers. Furthermore, servers with hardcoded binding information do not easily
adapt to configuration changes. If you move a server to a different host, you need to
recompile all of the clients with the server’s new host name. So DCE provides more
flexible ways for clients to obtain server bindings.
The standard way for clients to find servers is by using CDS and the server host’s
endpoint map. Figure 10-1 provides a high-level example of this method, showing how a
fictitious dictionary client application on host larry finds a dictionary server on host
curly.
Figure 10-1. Server Binding Information
CDS Server
Server Entry
1
2
DCE Host
Services
3
4
5
Dict Server
Spell Server
Stat Server
BBS Server
Services
DCE Host
Host: moe
Server Entry
Host: curly
Host: larry
Application Servers
Application Client
Dict Client
Dict Server 1015
Spell Server 1014
Stat Server 1013
BBS Server 1012
Server_Name Endpoint
Endpoint Map
Host: curly
Server: Dict Server
Transport: TCP/IP
1. When the dictionary server starts up, DCE host software assigns the server a
communications port (endpoint), which clients will use to communicate with this
server. Here, the endpoint is TCP/IP port 1015. The DCE host software also
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