| User interface basics / Connecting to a GUI front-end | |
When a program has started and the runtime system waits for a user action, but the end user does not do anything, the front end sends a 'ping' event every 5 minutes to keep the TCP connection alive. This situation can happen if the user leaves the workstation for a while without closing the application. The front end ping is a normal situation and part of the GUI client/server protocol. However, if the front end program is not stopped properly (when killed by a system reboot, for example), the TCP connection is lost and the runtime system does not receive any more 'ping' events. In this case, the runtime system waits for a specified time before it stops with fatal error -8063.
gui.protocol.pingTimeout = 800
By default, the runtime system waits for 600 seconds (10 minutes).
If you set this timeout to a value lower than the ping delay of the front-end, the program will stop with a fatal error after that timeout, even if the TCP connection is still alive. For example, with a front end having a ping delay of 5 minutes, the minimum value for this parameter should be about 330 seconds (5 minutes + 30 seconds to make sure the client ping arrives).