Host Timing Considerations

When you develop a host access application, your code must accommodate potential host processing delays for wait-dependent operations like connecting or sending a key. For such operations, your code must detect when the host finishes processing and is ready to receive more commands. Sending additional input before the host is ready will result in an error.

To allow you to reliably program for wait-dependent operations, Attachmate Verastream SDK for Unisys and Airlines objects include a variety of wait-related methods. Although all of these methods enable you to determine when the host is ready for input, each addresses a specific timing-sensitive situation. To help you program for these different situations, this topic discusses wait-related methods and how they can handle different wait modes.

Note Attachmate Verastream SDK for Unisys and Airlines also provides event handling functions that you can use for this purpose. For details, see Handling Events.

Common Wait Methods

Depending on the host processing situation, some wait methods are better than others at determining when the host is ready for input. Following are descriptions of the Attachmate Verastream SDK for Unisys and Airlines wait methods provided for Screen objects.

This method
waitForCursor For the host cursor to move to a specified location. This is useful for host applications that change the cursor location from screen to screen; however, it is useful only if you know what the cursor location will be.
waitForString Until a specified string appears on the screen. Although this is usually the most reliable method of waiting, it is practical only in cases where you are sure of the sequence of host screens.
waitHostQuiet Until there has been no activity in the host session for a specified amount of time, referred to as the settle time. The lower the settle time, the faster your application will run. The higher the settle time, the less chance there is for your application to send input before the host is ready. A workable settle time depends on the typical response time of your host application and network speed. Typically, one to two seconds works.
Related Topics
Common Tasks