Considerations When Advertising Legacy Services

Generally, modifying the source code to add SLP is preferable to writing a SLP-enabled service that uses the SLP API to advertise on behalf of other services. Modifying the source code is also preferable to using proxy registration. When you modify the source code, you can add service-specific features and closely track service availability. If the source code is unavailable, writing an SLP-enabled helper service that advertises on behalf of other services is preferable to using proxy registration. Ideally, this helper service is integrated into the service start/stop procedure that is used to control activation and deactivation. Proxy advertising is generally the third choice, when no source code is available and writing a standalone SA is impractical.

Proxy advertisements are maintained only if slpd is running to read the proxy registration file. No direct connection exists between the proxy advertisement and the service. If an advertisement times out or slpd is halted, the proxy advertisement is no longer available.

If the service is shut down, slpd must be stopped. The serialized registration file is edited to comment out or remove the proxy advertisement, and slpd is restarted. You must follow the same procedure when the service is restarted or reinstalled. The lack of connection between the proxy advertisement and the service is a major disadvantage of proxy advertisements.