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.