What are the License Server minimum requirements?

License Server requires Java 1.6 or newer to operate. License Server has been built to run on any modern server hardware.

Other minimum requirements include:

  • At least 50 MB of hard disk space for the main application.
  • The log file size and database size are dependant on License Server usage. We recommend keeping at least 1 GB of hard disk space available at any time. Setting the log level to debug or trace will have an impact on log file size.


License Server does not support IBM JDK. License Server shares the minimum requirements of Play2. Refer to https://www.playframework.com/documentation/2.3.x/Installing for more information.

Does JRebel 6 support License Server 2.x?

No. JRebel 6 requires License Server 3 or newer.

How long is a managed seat valid?

Managed seats are permanently assigned to developers – they will not be returned to the seat pool when the developer is not actively using their license.

The client checks against the server after every 60 minutes. If you have checked out an offline seat, the client will not ping the server while the offline seat remains valid (1 to 15 days).

How long is a floating seat valid? How often does the client talk to the server?

The main workflow of the client while communicating with the server to use the floating seat:

  1. Acquire a new lease at JVM startup or IDE startup (if the JRebel plugin is installed and JRebel activated).
  2. Update the existing lease once every 60 seconds.
  3. If the connection to the server is lost or the lease otherwise expires, try to recover it by acquiring a new lease from the server. Until it cannot be acquired, JRebel will be running without a valid license (with no reloading available).

So for an example, a series of licensing events during one JVM execution could look like that:

JVM startup
—> OK
[1 minute]
—> OK
[1 minute]
—> OK
[1 minute]
—> Update failed ; temporarily no license
—> OK
[1 minute]
—> OK
[20 seconds]
JVM shutdown by user

How are the floating seats returned to the server?

When you reach or approach to the maximum number of floating seats that your license allows you, you might wonder how the occupied seats are freed up by the server. These are the basic rules:

  • The JRebel client or the IDE pings the server every 60 seconds. After around 2 minutes of no pings received, the server will assume the client JVM was terminated and will free up the seat.
  • If somebody has taken out an offline token, it will only be returned after the offline token’s validity period has expired (default 24 hours, but up to 15 days) or when that client explicitly performs a -go-online action to release the seat.
  • If the client has somehow lost the seat (e.g. got disconnected for a couple of minutes), and the user tries to reload a class again, the JRebel client will automatically try to re-capture the seat. If the seats are now used up by somebody else on the server side – bad luck!

How can I use my product offline with License Server licensing?

For more information, please refer to the JRebel configuration chapter of this manual. Look up the relevant JRebel setup and look for info about going offline within the corresponding section.

Does ZeroTurnaround host a public instance of the License Server?

No. At the moment, ZeroTurnaround itself does not host a public License Server instance for everybody to use. This is also not planned for the foreseeable future.

Can I move a License Server installation?

Yes. You can move the License Server installation to a new machine or location. Follow these steps to achieve this.

  1. Copy the contents of the License Server folder (including the data folder) to the new location.
  2. Upon starting, License Server itself will need to be reactivated. This does not erase copied license and database information.
  3. All License Server users need to reactivate their JRebel or XRebel clients using the new License Server Group URL.

ZeroTurnaround permits a seven day transition period for moving a License Server installation. ZeroTurnaround monitors these events to prevent misuse.