Inet License Server


InetLicenseServer is a software program running as a service on a Windows server. It controls the allocation of user licenses to Inet/Winet programs running on client workstations. It also collects and stores information pertaining to connections made by the client workstations to application servers for example, mainframes running transversal systems. Information on assigned licenses and connections are made available as a CSV file for subsequent analysis and reporting.

The licensing system uses a loosely coupled model as opposed to a tightly coupled model. In the case of a tightly coupled system the application on the application server manages the allocation of licenses. When a session is established between the client and the server, the server application has complete control over allocating a license. In the case of Winet the application has no knowledge of the Winet licensing requirements. This means that a loosely coupled model must be used where a license server with little knowledge of the application must be used. This has implications in terms of the robustness of the entire system depending on license server accessibility which can be caused by hardware, software or network permanent or temporary problems.  

The License server does more than just managing licenses, it is also a system utilization and monitoring tool.


Whenever a Winet module (E.g. Inet3270.exe, the TN3270E terminal emulator) is started on a client PC, a TLS TCP connection is made to the License server and a license is requested. If one is available, it is allocated by the server and a connection can then be made to the application server e.g. a mainframe running a transversal system.

user license is defined by a user id which is the combination of the MAC address of the workstation and the username of the user. Each user license is allocated in a slot which is represented by a number. There can be more slots than the available licenses.

The grace period is the time during which a user can use a license regardless of the availability of access to the License server. During the grace period the License server must reserve allocated licenses so that information being sent to the server can be updated. Every time a workstation interacts with the License server, the grace period is updated. Interactions happens when a Winet program (for example the Inet2370 terminal emulator) is started, opens a connection, closes a connection, receives a TCP error, receives a Telnet error, refreshes the server session and exits the program. When all licenses are allocated and a new request is issued, the oldest slot not in the grace period is re-allocated. If there is no available license that is in the grace period, an error is sent to the requesting application and it can no longer make connections to the application server e.g., the transversal mainframe application.

The default grace period is 30 days, but it can be configured to a shorter time. The shorter the grace period, the more vulnerable the system is to License server non-accessibility.

Information collected by License server

Information is collected for each slot not being re-allocated whether in or out of the grace period. The following events are recorded:

Program startup

Program exit

Connection success

TCP (network) error (e.g., connection timeout)

Telnet negotiation error (e.g., Device in use)

Connection closed by user

Connection closed by application server

The events are per Winet application e.g., Inet3270 and per configuration (e.g., terminal or printer) used.

For each event the following information is stored: Slot number, IP address, MAC address, User name, Winet program name, Winet program revision with compile date and time of various components, Configuration, mainframe address and port, LU assigned, Count of events, IP address redirected from fallback License server, event type, error if any, license information, SSL/TLS version, Windows versions, the current number of simultaneous connections to the License server and the maximum simultaneous connections.

Fallback License server

A fallback License server can be installed to take over the functions of the main License server if the latter can’t be accessed. As soon as the main license server can be accessed again, it will continue to provide the functionality.

Benefits of a longer grace period

The access to the mainframe is guaranteed for a longer time.

The negative aspect is that the maximum number of user licenses may need to be increased when there are many more users than the available licenses. In the end the choice of the grace period depends on a tradeoff between robustness and functionality and the number of licenses. A minimum grace period of 7 days is recommended.

InetLicenseServer Installation

Any Windows Server Machine or Windows PC can be used. This machine must be accessible by all Winet PC’s.