Add more NetworkMonitor examples

[erlingrj]

This PR adds two new NetworkMonitor examples

[erlingrj]

@edwardalee here is the work I have done on Network Monitoring. I am tagging you here so you can have a look and possibly give some feedback. In any case, we can discuss this on our next meeting. Perhaps it should live in a separate repo, and not in lf-demos, what do you think?

I had trouble running the Probe4.lf and Probe5.lf on my Macbook. They work as non-federated, but with federated they just terminate immediately, no logging output is printed. Very strange

[edwardalee]

Looks very cool! Probe4.lf doesn't compile for me, however:

/Users/edwardlee/git/lf-demos/network-monitor/fed-gen/Probe4/src-gen/federate__m__0/./_simplehttpserver.h:6:10: fatal error: 'microhttpd.h' file not found
#include <microhttpd.h>
         ^~~~~~~~~~~~~~
1 error generated.

I think maybe it's missing a cmake-include?

Also, the HTTP server looks nice. I've been meaning to turn the reactors here into a Lingo package. This would also enable a web socket connection. Should we use those? I haven't compared to yours...

[erlingrj]

Looks very cool! Probe4.lf doesn't compile for me, however:

/Users/edwardlee/git/lf-demos/network-monitor/fed-gen/Probe4/src-gen/federate__m__0/./_simplehttpserver.h:6:10: fatal error: 'microhttpd.h' file not found
#include <microhttpd.h>
         ^~~~~~~~~~~~~~
1 error generated.

I think maybe it's missing a cmake-include?

Also, the HTTP server looks nice. I've been meaning to turn the reactors here into a Lingo package. This would also enable a web socket connection. Should we use those? I haven't compared to yours...

Did you install libmicrohttpd with brew install libmicrohttpd? On my MacBook it was installed to /usr/local and thus in HttpServer.cmake I update include directories and link directories correspondingly. You can check where it was installed with sudo find / -name "microhttpd.h"

[edwardalee]

Did you install libmicrohttpd with brew install libmicrohttpd? On my MacBook it was installed to /usr/local and thus in HttpServer.cmake I update include directories and link directories correspondingly. You can check where it was installed with sudo find / -name "microhttpd.h"

Yes, I installed it. The .h file ends up here: /opt/homebrew/include/microhttpd.h. Maybe there is some cmake magic that will find this? Otherwise, I guess some environment variable needs to be set explicitly.

[erlingrj]

Did you install libmicrohttpd with brew install libmicrohttpd? On my MacBook it was installed to /usr/local and thus in HttpServer.cmake I update include directories and link directories correspondingly. You can check where it was installed with sudo find / -name "microhttpd.h"

Yes, I installed it. The .h file ends up here: /opt/homebrew/include/microhttpd.h. Maybe there is some cmake magic that will find this? Otherwise, I guess some environment variable needs to be set explicitly.

Could you try once more. I tried adding /opt/homebrew to the path CMake searches for libraries.

[erlingrj]

Also, the HTTP server looks nice. I've been meaning to turn the reactors here into a Lingo package. This would also enable a web socket connection. Should we use those? I haven't compared to yours...

I had a look at ServerUI.lf and it is more general. But I think it is wiser to build on a well-established library, e.g. libmicrohttpd. A quick inspection and it looks like there is a race condition. If the user requests e.g. /foo, the listening thread will schedule a physical action and then go back to accept(). If a new request is accepted, then this will overwrite browser_ui->client_socket, which is used by the reaction triggered by the response port.

Wouldnt it be easier to let a library handle the sockets and threads?

[erlingrj]

Perhaps a compromise, where I implement the generality of your proposal (i.e. the base HTTP reactor outputs requests on its output port and responds with whatever it receives on its input port), but base it off libmicrohttpd?