To establish and maintain a connection to an application server, a client application uses one or more connection components. You can find these components on the DataSnap or WebServices category of the Tool Palette. 

Use a connection component to

• Identify the protocol for communicating with the application server. Each type of connection component represents a different communication protocol. See Choosing a connection protocol for details on the benefits and limitations of the available protocols.
• Indicate how to locate the server machine. The details of identifying the server machine vary depending on the protocol. See the following topics for details:
• Specifying a connection using DCOM
• Specifying a connection using sockets
• Specifying a connection using HTTP
• Specifying a connection using SOAP
• Identify the application server on the server machine.
• If you are not using SOAP, identify the server using the ServerName or ServerGUID property. ServerName identifies the base name of the class you specify when creating the remote data module on the application server. See Setting up the remote data module for details on how this value is specified on the server. If the server is registered or installed on the client machine, or if the connection component is connected to the server machine, you can set the ServerName property at design time by choosing from a drop-down list in the Object Inspector. ServerGUID specifies the GUID of the remote data module's interface. You can look up this value using the type library editor.
• Manage server connections. Connection components can be used to create or drop connections and to call application server interfaces.

If you are using SOAP, the server is identified in the URL you use to locate the server machine. Follow the steps in Specifying a connection using SOAP. 

Usually the application server is on a different machine from the client application, but even if the server resides on the same machine as the client application (for example, during the building and testing of the entire multi-tier application), you can still use the connection component to identify the application server by name, specify a server machine, and use the application server interface.