XPLM_API XPLMPluginID XPLMFindPluginBySignature(
                         const char *         inSignature);    

This routine returns the plug-in ID of the plug-in whose signature matches what is passed in or XPLM_NO_PLUGIN_ID if no running plug-in has this signature. Signatures are the best way to identify another plug-in as they are independent of the file system path of a plug-in or the human-readable plug-in name, and should be unique for all plug-ins. Use this routine to locate another plugin that your plugin interoperates with