WebExp2 Experimenter's Manual - School of Informatics - University ...

9 Troubleshooting
If you have trouble, there is usually plenty of information giving you hints about what might be wrong, or at
least where the problem is. Java will tell you of any ‘runtime errors’, and WebExp2 will let you know if anything
goes wrongly or unexpectedly within the program.
The first place to look if you have trouble (for example, if the experiment won’t start, or it fails) is at the
console output of the system. Messages are generated both to report errors and to describe the progress of
an experiment, and these messages are output to a console for both the server and clients. Ultimately this
information is logged to a file which is available to the server. Section 8.3 describes the type of messages that
are generated.
9.1 Client messages
Client output goes to the Java console, which is not displayed by default but may usually be opened either from
the browser (although note that Firefox for some reason has failed to include this option) or from an icon (in
the system tray in Windows). If a participant reports problems you may be able to get them to open the Java
console and see what output has been generated describing the problem.
Note: Currently you will only receive logs for completed experiments. Eventually output for uncompleted
experiments will also be sent back to the server so it will be easier to analyse problems.
9.2 Server messages
Server output goes directly to the console in which you run the server, so you can check this at any time for
problems. Due to the limited size of a console buffer however, older messages will eventually be lost as new ones
are generated.
Note: The server is prevented from saving its own log files at the moment, until the system can be extended to
manage the increasing size of a log file while a server continues to run. Messages are still generated and printed
to the console however.
9.3 Common problems
This section describes problems which may crop up more regularly, and which have simple solutions — they
may be due to a problem with your server setup or an error in the experiment description. This list will be
expanded
Mismatched ports
starting your server.
Make sure the port specified in your applet parameter is the same as the one used when
9.4 Experiment/Client problems
If you have problems running an experiment at the client end (i.e. in a browser) then you can first open the
Java console (from a browser menu, or via a system tray icon in Windows) and see if it reports any runtime
errors. It should also give you feedback while the experiment is running. This information is logged and sent
back to the server at the end of an experiment.
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