Unable to move cursor outside input capable fields
The concept of a cursor to a browser only applies when working with input capable fields. Since the browser does not understand the concept of cursor positioning outside input fields can be used to indicate valuable positioning information, they do not allow users to place a cursor on output only fields. This means that you cannot move the cursor to a screen location that contains an output field and press an AID key to trigger a cursor sensitive AS/400 action.
There is no field exit key
Seasoned AS/400 users expect several things to happen when they press the field exit (or field minus) key in a non HTML based emulation package. Some of the expected behavior includes clearing out the remaining characters in the field, performing any necessary editing adjustment (e.g., right adjust - blank fill) and to move the cursor to the beginning of the next field. Since Webulator/400 is a form processing script program, it cannot provide all of the field exit functionality in real time. If a user could press field exit using Webulator/400, it would not be able to clear out the remaining data in the field nor could it immediately perform necessary adjustments (Webulator/400 always performs editing functions on all data it receives from the browser). The only functionality remaining is to move the cursor to the beginning of the next field. In other words, there is no difference between a field exit key and a tab key when using Webulator/400.
Unable to view all AS/400 output messages
Since the browser is only able to receive data from the AS/400 after a user submits the HTML form, it is not possible for Webulator/400 to continually send screen updates to the browser. Webulator/400 will attempt to buffer all output messages and send them with the next screen but it is not always able to do so. Webulator/400 clears all screen data (seen and unseen) whenever it encounters a Clear Unit command in the 5250 data stream. A Clear Unit command is inserted into the 5250 data stream by various screen I/O commands such as the EXFMT command in RPG. In addition, Webulator/400 is also unable to support AS/400 Break messages. AS/400 Break messages are messages that interrupt the current screen and require some sort of response (at a minimum an Enter key) to return to the previous screen. Break messages cause Webulator/400 to be out of sync with the AS/400 causing unpredictable results.
Extra screens are occasionally sent to the browser
Some host programs send a write/read screen I/O request followed immediately by a cancel read operation. The end result of these operations are the same as a write request. These requests are handled seamlessly by non HTML based emulators because of their constant communication link with the AS/400. Webulator/400 has a little more difficulty handling these I/O requests. Webulator/400 will verify that no Cancel requests have been generated by the AS/400 before sending a screen to the browser. Unfortunately, there is no guarantee that the Cancel request will be received before the screen is sent to the browser. This means that certain write/read/cancel requests will get by Webulator/400's checking and be sent to the browser. If this happens, all you have to do is press a Virtual Keyboard button and the next screen will be sent to the browser.
Unable to perform Text Assist functions
Webulator/400 is unable to fully support programs that use the Text Assist functions (e.g., OfficeVision/400). Text Assist programs require more interaction with the AS/400 than is possible using Webulator/400.
The Attention button does not always work
Care should be taken before allowing this button to be made available through Webulator/400. You must ensure that the user profile that is signed on for a session has an Attention program assigned to it. As long as it does, everything will work fine. You will run into problems if a Webulator/400 user presses the Attention button and their user profile does not have an attention program defined for it. 5250 emulation programs are able to notify the AS/400 that the Attention key was pressed and retain control of the current screen until they are interrupted by the new attention program. If there is no attention program to run, the 5250 emulation program will continue to process the current screen. Since the Web browser returns control to the AS/400 when any submit button is pressed (including the Attention submit button), it must wait for a new screen to arrive from the AS/400 before allowing the user to interact with the screen. If there is no attention program to generate a new screen, the browser will time out waiting for the new screen and will not allow the user to continue with the screen where the Attention button was pressed.