How to set HTTP status in from serverinterface/queryhandlers

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Serge A asked Mar 8, '24 Serge A commented Mar 19, '24

How to set HTTP status in from serverinterface/queryhandlers

We use custom query handlers in MAIN:/project/exec/globals/serverinterface/queryhandlers to interact with our models via FlexSim Webserver, as documented in https://docs.flexsim.com/en/24.0/Reference/DeveloperAdvancedUser/Webserver/Webserver.html#InstanceQueries

What I noticed is that queryinstance always responds with HTTP status code 200 OK, and there doesn't seem a way to set a different status. In particular I'd like to be able to reply with 400 Bad Request or 404 Not Found.

I noticed than many default queryhandlers use this or similar code:

setnodestr(replyNode, "HTTP/1.1 404 Not Found");
return replyNode;

However, if I try to do the same and set replyNode to be the header of the response, it still ends up as the body of the response with a status 200.

For instance, this HTTP request

http://127.0.0.1:10001/webserver.dll?queryinstance=TestModel&instancenum=1&getnodedata=doesnotexist

results in a response with HTTP status code 200 and the body fakes to be an HTTP response:

So the question is, what is the correct way to set HTTP status code from the instance query handler?

FlexSim 24.0.2

Software Version:

FlexSim 24.0.2

flexsim webserver http queryhandler

1709896897369.png (72.1 KiB)

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Jeanette F ♦♦ commented · Mar 14 at 06:16 AM

Hi @Serge A, was Jacob Gillespie's answer helpful? If so, please click the "Accept" button at the bottom of their answer. Or if you still have questions, add a comment and we'll continue the conversation.

If we haven't heard back from you within 3 business days we'll auto-accept an answer, but you can always comment back to reopen your question.

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Answer 1 · 2024-03-08T23:40:41Z

Jacob Gillespie answered Mar 8, '24 Serge A commented Mar 19, '24

@Serge A

It looks like we accidentally removed some new line characters that our code was relying on to check for a valid http header.

It used to be like this:

setnodestr(replyNode, "HTTP/1.1 404 Not Found\r\n\r\n");

When replyNode has byteblock data it first looks for a valid http header. If it finds a valid header it just sends it straight through to the client.

Sorry, this probably would have been useful to know for your previous question about sending JSON text.

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Serge A commented · Mar 19 at 08:34 AM

Thank you @Jacob Gillespie , this solution is working perfectly. And indeed, it's also useful to sending application/json responses.

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