UPNP_E_OUTOF_SOCKET signifies that the SDK cannot create any more sockets. This occurs in any function that makes network connections, such as discovery (e.g. UpnpSearchAsync or UpnpSendAdvertisement), control (e.g. UpnpSendAction), eventing (e.g. UpnpNotify), and HTTP functions (e.g. UpnpDownloadXmlDoc).