Figure 1 shows an example installation; the server is running on sgibox, with two cyslice licenses issued to applications running on sgibox2 and ntbox. Also shown is the license manager, hlmanager which the system administrator can use to remotely control some aspects of the operation of the license server.

The link between the license server and applications is via connected TCP/IP sockets. This means that a connection has to be maintained at all times during the life of an application, and if its broken the application loses its license and will exit. See Application Restore for details on how users can enable the restore function.

Compared to Node-Locked Licenses

When a host is issued a node-locked license, any number of users can run any number of associated applications on that host. For example, with a single cyslicev3 license, any number of CySlices and PlyTools can be run on the licensed host. In fact, CySlice itself is really two applications - the GUI and the graphics window are separate programs - and so when running just one CySlice you are running at least two programs off the one license.

Floating licenses have been designed to operate in the same way. The first application to run on a host will grab the first available floating license. More applications can then be run on that host without the need to grab more licenses; they will attach themselves to the first floating license. Even if the first application exits, as long as some applications are running, the floating license will still be in use.

For example, if Cyslice is run from a floating license, it will grab the first available cyslicev3 license. If PlyTool is then run, it will attach itself to the cyslicev3 license and be able to run. Only one floating license is in use even though two applications are running.

If the user then exits from CySlice, PlyTool still has the floating license and continues to run. What they shouldn't do then is lock their office and go on a holiday because no-one else will be able to use that floating license while they are away! Fortunatly, the license manager lets sysadmins and other trusted users reclaim licenses that have been grabbed but not returned.

Choosing a Server Host

The following is a list of points you should consider when choosing a server host:

1. It should be stable. If the server goes down often then you will have an angry crowd outside your door very soon.
   
   
2. Ideally it would have plently of free RAM. If the server is heavily loaded with many RAM intensive processes, the OS will swap out low usage applications like hlserver, and the response time to license requests could be increased. Licenses are checked often throughout the running of an application, so if license requests are slowed the user could experience a reduction in the application performance.
   
   
3. It should be on a high speed link to the served hosts. 10Mbit ethernet is perfectly OK, but PPP over a loaded modem connection is probably not. Again, if the license checks are slowed, the application performance will suffer.
   
   
4. It should be a long term installation. The license server application has a node locked license to the server host. If you change the host, a fee will be charged for each re-issue of the server license based on the floating licenses it servers. If you anticipate changing the host in the near future, let us know and we will issue you a time limited license and a free re-issue when then new host is up and running.

Supported Platforms

HLServer now runs on IRIX, Linux and Windows NT/2K/XP platforms, and will issue licenses to IRIX, Linux and Windows NT/2K/XP applications.