One machine for one student sends null LTI request

[ChrisRiesbeck]

Looking for any ideas on possible causes of an LTI access problem.   One student trying to access my Java server on his laptop sends a bad LTI request. When he uses his desktop at home he connects fine.  Hundreds of students for over a decade have not had this problem.  What might be different on his laptop that could lead to a different LTI request being sent?  Some port firewall?

[chriscas]

Hi @ChrisRiesbeck,

To start with, is this an LTI 1.1 or LTI 1.3 launch that is having the issue?  In addition, do you know what browser and operating system/device the problematic launch is occurring from?  When you sai it's a null request, does your srver truly receive nothing, or is there a specific parameter you're lloking for that's not included in the launch?

My first guess as to local issues on the student's device would be some kind of ad/content blocking extension installed int he browser.  The second could be the browser itself (maybe a privacy-oriented browser blocking too much info itself).  Without knowing the exact problem at this point, perhaos it could be a DNS problem, or an SSL certificate issue.  Just kind of throwing out some potential causes...

If this is an LTI 1.3 launch from a chromium-based browser, there is an LTI debugger extension available which you could have the student install and perhaps check via a screen share session.  The extension will show you what the browser should be sending, which you could match to what your server is receiving to potentially narrow down the issue...

I hope some of this might help a bit!  Please do post back here when and if you're able.

-Chris

[ChrisRiesbeck]

Thanks for the suggestions, Chris.  It's LTI 1.1 -- very old Java code.I get a request but HttpServletRequest.getQueryString() returns null.

I've asked the student to try a different browser. I'll also ask if the machines differ in OS or browser.  I've never had this issue with either OS or any browser, and 50 other students this term have had no issue, so some personal configuration seems more likely than something with server or network.

Thanks again.

[ChrisRiesbeck]

His laptop is MacOS Tahoe 26.0.1. The  problem happens on both Chrome and Safari. Whenever he clicks the link to open my website in a new window -- which is what everyone does -- he gets the server error because my server doesn't see anything in the query string. That would seem to rule out a browser-specific issue.

Everything works on his Windows desktop. I don't know what browser but Chrome or Edge seems most likely. That would seem to rule out a Canvas setting of his. 

MacOS + Chrome is probably the most common combination with my students, and myself, none of whom have this problem. 

I'm stumped what else to check for.