Hi all,
After some issues spending 1 week to get HTTP embedded server working in LV for a single application, I have some remarks that might trigger some need to a more flexible, simple and open HTTP configuration. The current implementation of a HTTP server is quite limited and outdated to my opinion.
First thing is the NI Web Server. This is a nice feature, however, NI recommends using it rather then the outdated Application Web Server but the problem is that this thing is only a single server running on a single port (for every application executable). Good enough for a single web server on a host using a web browser but how about implementing a LV HTTP server for each application (e.g. RPC server)? To my knowledge, every other programming language (e.g. Python, C++, ...) has a core implementation for this.
I have spent a lot of time to see what the best solution is for implementing a HTTP server belonging to a single application executable in LV. This executable is typically a application GUI or a backend service in our projects and we have a lot of them. Every application needs its own RPC server (running on a different port) and hence running its own RPC methods and I ended up implementing a Web Service using a LV Application Web Server, I can't see other ways at this moment using core LV functionality without the need for additional packages to install.
I also miss the enabling and disabling of the HTTP server during runtime. As in our project applications, we also have other transport layers for implementing RPC, such as zeroMQ (thanks to Martijn Jasperse's library on VIPM) and TCP (native built-in to LV). I would like to run only one of these transport services by configuration but here is a second problem here, once the application is running, the HTTP Web Service automatically registers and there is no controlled way for disabling it during runtime, which gives me headaches since I have to change the port number as another transport layer cannot use the same port as the HTTP server. One might say to built another application (actor based) exe and implement the Web Service from there in a different actor but this is a pain in the *** to have 2 exe's for each single application. Why can't the HTTP Web Service not switched OFF and ON again, both in development and runtime? I found a property node to disable the server but it apparently doesn't work (seems related to the native panel web server).
One of the major disadvantages that I also encountered is the HTTP methods that are programmed in a single VI and there is no way to pass data to these method VI's (like using actor framework or even classes in general). It seems we have to use FGV's (Functional Global Variables) to share data between my main application actor and these HTTP method VI's itself. Even then, the HTTP Service Request refnum is only valid in the HTTP method VI itself, once it finished executing, the refnum is flushed and not valid anymore, so no way to pass this refnum using actor framework messages to my application actors. That's quite frustrating since I have to use notifiers within the HTTP method VI's instead as a plan B backup solution signifying that the method VI can proceed and finish its execution once it Wait on Notifier function is complete (since I want to send an answer from my application actors, not from the HTTP method itself)!
Another issue I observed is that I can't "Start" the HTTP Web Service from the right-click menu in the project explorer, it simply crashes with some dubious error that the 'system is currently in an invalid state for the current message'. What does this mean, no clue from NI help docs?
I can only right-click and select "Start (Debug Server)" to make it work (but on the debug port 8001 by default). All other options just fail, the same for "Publish", it simply doesn't work in my LV2020 SP1 (32-bit) version and I have no clue why as there is not a single error message at all!
Also, why must we use MS Silverlight to control application webservers from LV? Silverlight is deprecated and I ended up using MS Edge in "Internet Explorer" mode to get the config page working (after spending another two hours to find out). Even then, some config panes just show up with error dialogs and no way to see active services being registered by the application HTTP web server. In the end I just used TCP View to see active services running. It is always frustrating to use third party apps to do simple things.
As you might notice from this message, I suffered a lot of days to figure out how to implement HTTP in a simple decent way using LV's core HTTP functionality. I wonder if this will be better using LV 2024 Q1?
If anyone has ideas on how to properly configure multiple application HTTP servers for each application on different ports while controlling itself, please share it with me. I am open to any idea's and wonder if there are other solutions for HTTP implementation (not using 3rd party packages). To my opinion, HTTP should be easy and open to configure properly in LV without a lot of current non-working Web Server issues.
Please note that I tried to reinstall the NI Web Server and other web service related stuff using NI package manager but no avail.
Best Regards,
Davy Anthonissen
