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    Reply  11 Feb 2020, Berta Beltran, Bug Report, Compiling Midas in OS 10.15 Catalina  
> > Any luck with Midas in OS 10.15? 
> 
> Best I can tell, the problem is not in midas: pthread.h should be there, somewhere.
> 
> K.O.


HI Konstain, 

Thanks for your reply. I have been investigating this issue of pthread in OS 10.15.  Found this forum post 
https://github.com/wjakob/nori/issues/16

that seem to suggest that pthread.h is in a different directory from OS 10.14 and on. And the end of the post the 
developer suggests that he has found a way to fix the Cmake to work so I have checked his code updates in here 
https://github.com/wjakob/nori/commit/be46cccc01a75b21dad1a3f61baa108fe644fc4b

I have added his lines 


if(APPLE)
   # Try to auto-detect a suitable SDK
   execute_process(COMMAND bash -c "xcodebuild -version -sdk | grep MacOSX | grep Path | head -n 1 | cut -f 2 -
d ' '" OUTPUT_VARIABLE CMAKE_OSX_SYSROOT)
   string(REGEX REPLACE "(\r?\n)+$" "" CMAKE_OSX_SYSROOT "${CMAKE_OSX_SYSROOT}")
   string(REGEX REPLACE "^.*X([0-9.]*).sdk$" "\\1" CMAKE_OSX_DEPLOYMENT_TARGET 
"${CMAKE_OSX_SYSROOT}")
 endif()

to my local pakages/midas/CMakeLists.txt and run cmake .., make install again but now I get a different error 

[  1%] Building CXX object CMakeFiles/mfeo.dir/src/mfe.cxx.o
clang: error: invalid version number in '-mmacosx-version-
min=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/DriverKit19.0.sdk'
clang: warning: using sysroot for 'DriverKit' but targeting 'MacOSX' [-Wincompatible-sysroot]


I will continue investigating this issue tomorrow, but please let me know if you have any suggestions.

Also my version of cmake is 3.16.3

Thanks 

Berta 
    Reply  11 Feb 2020, Berta Beltran, Suggestion, switch midas to c++ threads? 
> Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
> switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
> threads are a layer on top of pthreads, the best I know).
> 
> This should remove the dependency on pthreads.h and use a more native implementation of 
> threads on MacOS and Windows. (again, the best I can tell).
> 
> Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
> with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
> bedeviling midas in the early days (and still happens today!). Current midas kills everything 
> after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
> has core dumps to look at. (to see which program/thread holds the lock and would not give it 
> up).
> 
> Any thoughts on this?
> 
> K.O.

Hi, I just wanted to say that I have seen this post and maybe that is the solution to the pthreads compiler problem in OS 10.15, but 
of course I am a total amateur in here. Thanks for thinking about this and I will wait and hold to see what gets decided. Thanks

Berta  
    Reply  12 Feb 2020, Berta Beltran, Bug Report, Compiling Midas in OS 10.15 Catalina  
> For your reference, here on my MacOSX 10.14.6 with XCode 11.3.1 the pthread.h file is present in locations listed below.
> 
> Did you execute "xcode-select --install" ?
> 
> 
> ~$ locate pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread.h
> /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
> /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread.h

Hi Stefan,

Thanks for looking into this. Yes, I have done  "xcode-select --install"

This is my output when I try to locate pthread.h

Darrens-Mac-mini:~ betacage$ locate pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/pthread/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/pthread/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/pthread.h

and this is what I see in my SDKs folder 

Darrens-Mac-mini:SDKs betacage$ pwd
/Library/Developer/CommandLineTools/SDKs
Darrens-Mac-mini:SDKs betacage$ ls
MacOSX.sdk	MacOSX10.14.sdk	MacOSX10.15.sdk

So it looks like in this computer one needs to read the version of the SDK as pthread.h is not in MacOSX.sdk but in MacOSX10.15.sdk

Thanks 

Berta 
    Reply  12 Feb 2020, Berta Beltran, Bug Report, Compiling Midas in OS 10.15 Catalina  
> Another thought: Can you delete the midas build directory and run cmake again? Like
> 
> $ cd midas/build
> $ rm -rf *
> $ cmake ..
> $ make VERBOSE=1
> 
> If you have the old build cache and upgraded your OS in meantime, the cache needs to be rebuild. The VERBOSE 
> flag tells you the compiler options, and you see where the compiler looks for the SDK directory.
> 
> Cheers,
> Stefan

Hi Stefan, 

Thanks again for your reply. Yes! the suggestion of rebuilding the cache was the right one, this is the output of cmake ..

Darrens-Mac-mini:~ betacage$ cd packages/midas/build/
Darrens-Mac-mini:build betacage$ rm -rf *
Darrens-Mac-mini:build betacage$ cmake ..
-- MIDAS: cmake version: 3.16.3
-- The C compiler identification is AppleClang 11.0.0.11000033
-- The CXX compiler identification is AppleClang 11.0.0.11000033
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- MIDAS: CMAKE_INSTALL_PREFIX: /Users/betacage/packages/midas
-- MIDAS: Found ROOT version 6.18/04
-- Found ZLIB: /usr/lib/libz.dylib (found version "1.2.11") 
-- MIDAS: Found ZLIB version 1.2.11
-- Found OpenSSL: /usr/lib/libcrypto.dylib (found version "1.1.1d")  
-- MIDAS: Found OpenSSL version 1.1.1d
-- MIDAS: MySQL not found
-- MIDAS: ODBC not found
-- MIDAS: SQLITE not found
-- MIDAS: nvidia-smi not found
-- Setting default build type to "RelWithDebInfo"
-- Found Git: /usr/bin/git (found version "2.21.1 (Apple Git-122.3)") 
-- MIDAS example/experiment: MIDAS in-tree-build
-- MIDAS: Found ZLIB version 1.2.11
-- MIDAS example/experiment: Found ROOT version 6.18/04
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/betacage/packages/midas/build


Unfortunately running make VERBOSE=1 the compilation crashes, with the following error 

[ 39%] Linking CXX executable mhttpd
cd /Users/betacage/packages/midas/build/progs && /Applications/CMake.app/Contents/bin/cmake -E cmake_link_script CMakeFiles/mhttpd.dir/link.txt 
--verbose=1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++  -O2 -g -DNDEBUG -isysroot 
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -Wl,-search_paths_first -Wl,-
headerpad_max_install_names  CMakeFiles/mhttpd.dir/mhttpd.cxx.o CMakeFiles/mhttpd.dir/mongoose6.cxx.o CMakeFiles/mhttpd.dir/mgd.cxx.o 
CMakeFiles/mhttpd.dir/__/mscb/src/mscb.cxx.o  -o mhttpd  ../libmidas.a /usr/lib/libssl.dylib /usr/lib/libcrypto.dylib -lz 
ld: cannot link directly with dylib/framework, your binary is not an allowed client of /usr/lib/libcrypto.dylib for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [progs/mhttpd] Error 1
make[1]: *** [progs/CMakeFiles/mhttpd.dir/all] Error 2
make: *** [all] Error 2


Libcrypto seems to be part of the OpenSSL, so I am back to the original problem again. I did install OpenSSL via MacPorts. 

I have found this tread regarding this problem. But have to go and pick up my kids from school, so I don't have time to investigate today.
https://stackoverflow.com/questions/58446253/xcode-11-ld-error-your-binary-is-not-an-allowed-client-of-usr-lib-libcrypto-dy

Thanks again for staying with me and for responding so promptly. 

Berta 
    Reply  13 Feb 2020, Berta Beltran, Bug Report, Compiling Midas in OS 10.15 Catalina  
> Now you are stuck with openssl, which is optional for mhttpd. If you only use mhttpd locally, you maybe don't need SSL support. In that case you can jus do
> 
> [midas/build] $ cmake -D NO_SSL=1 ..
> 
> To disable that. If you do need SSL, maybe you can try to install openssl11 via mac ports.
> 
> Stefan

Thanks Stefan. 
If I run the compilation with the flag NO_SSL it works just fine. Still I think that Mhttpd is going to be important for us in the future as we may want to control the experiment remotely, so I will keep trying. But at least I 
can get started.

Thanks 

Berta 
    Reply  03 Mar 2020, Berta Beltran, Bug Report, Compiling Midas in OS 10.15 Catalina  
Thanks Konstantin,

I will keep an eye for the next release so that I can update my Midas to include ssl libraries.

Thanks 



> > > [midas/build] $ cmake -D NO_SSL=1 ..
> > If I run the compilation with the flag NO_SSL it works just fine. ...
> 
> FYI, the mongoose616 branch now has support for using the mbedtls https library,
> this library seems to build easily from sources and removes our dependency
> on where/how/which openssl library is installed. I hope to have this included
> in the next release of midas.
> 
> K.O.
    Reply  29 Aug 2019, Ben Smith, Forum, History plot problems for frontend with multiple indicies 
Hi Nick,

I confirm that this issue appears when using the MIDAS history driver. The issue does not appear when using the MYSQL history driver.

One solution is to give each frontend instance a different Event ID (see example code below for doing this in frontend_init). The history system did still seem to be confused by the existing FeDummy equipments/events even after making this change. However, after changing EQ_NAME from FeDummy to FeDum (i.e. starting from a clean state history-wise) things behaved normally.

I will note that some experiments definitely have a need for the "-i" method, especially those that run on distributed clusters.

Ben


```
INT frontend_init()
{
   sprintf(eq_name, "%s%02d", EQ_NAME, get_frontend_index());

   // Ensure each FE gets a different Event ID in the history system (951, 952 etc)
   char keyname[128];
   HNDLE hkey;
   int status;
   sprintf(keyname, "/Equipment/%s/Common/Event ID", eq_name);
   status = db_find_key(hDB, 0, keyname, &hkey);
   if (status != DB_SUCCESS) abort();

   WORD new_ev_id = 950 + get_frontend_index();
   status = db_set_data_index(hDB, hkey, &new_ev_id, 2, 0, TID_WORD);
   if (status != DB_SUCCESS) abort();
   return SUCCESS;
}
```
    Reply  02 Sep 2020, Ben Smith, Forum, Transition status message 
The information you want is in the ODB:
* "/System/Transition/status" is the overall integer status code.
* "/System/Transition/error" is the overall error message string.

There is also per-client status information in the ODB:
* "/System/Transition/Clients/<client_name>/status"
* "/System/Transition/Clients/<client_name>/error"
    Reply  29 Sep 2020, Ben Smith, Forum, using python client to start and stop run 
The ODB variable "/Runinfo/State" is a symptom of starting/stopping a run, rather than the cause.

In C++, one uses `cm_transition()` to start/stop runs.

In python code you can use the `start_run()` and `stop_run()` functions from `midas.client`: https://bitbucket.org/tmidas/midas/src/00ff089a836100186e9b26b9ca92623e672f0030/python/midas/client.py#lines-793:808
    Reply  01 Dec 2020, Ben Smith, Forum, subrun  
We use the lazylogger for something similar to this. You can specify the path to a custom script, and it will be run for each midas file that gets written:
https://midas.triumf.ca/MidasWiki/index.php/Lazylogger#Using_a_script
This means that you don't have to wait until the end of the run to start processing.

If the ROOT conversion is going to be slow, but you have a batch system available, you could use the lazylogger script to submit a job to the batch system for each file.

> 
> > Hi,
> > 
> > I was wondering if there is a "mechanism" to run an executable
> > file after each subrun is closed...
> > 
> > I need to convert .mid.lz4 subrun files to ROOT (TTree) files;
> > 
> > Thanks,
> > Gennaro
    Reply  12 Apr 2021, Ben Smith, Forum, Client gets immediately removed when using a script button. 
> if I use the script button, the logic_controller program is immediately deleted by MIDAS.

This is indeed very curious, and I can't reproduce it on my test experiment. Can you redirect stdout and stderr from the logic_controller program into a file, to see how far the program gets? If it gets to the while loop at the end, then it would be useful to add some debug statements to see what condition causes it to exit the loop.

Are there any relevant messages in the midas message log about the program being killed? What's the value of "/Programs/logic_controller/Watchdog timeout"? 
    Reply  12 Apr 2021, Ben Smith, Forum, Client gets immediately removed when using a script button. 
I think it would be useful to find the minimal example that exhibits this behaviour.

What happens if your logic controller code is simply the 17 lines below? What happens if you create another script button that only starts the logic controller, not any of the other programs? etc. Gradually re-add features until you hit the problem (or scream in horror if it breaks with 17 lines of C++ and a 1 line shell script).



#include "midas.h"
#include "stdio.h"

int main() {
   cm_connect_experiment("", "", "logic_controller", NULL);

   do {
     int status = cm_yield(100);
     printf("cm_yield returned %d\n", status);
     if (status == SS_ABORT || status == RPC_SHUTDOWN)
       break;
   } while (!ss_kbhit());

   cm_disconnect_experiment();

   return 0;
}
Entry  06 May 2021, Ben Smith, Info, New feature in odbxx that works like db_check_record() 
For those unfamiliar, odbxx is the interface that looks like a C++ map, but automatically syncs with the ODB - https://midas.triumf.ca/MidasWiki/index.php/Odbxx.

I've added a new feature that is similar to the existing odb::connect() function, but works like the old db_check_record(). The new odb::connect_and_fix_structure() function:
- keeps the existing value of any keys that are in both the ODB and your code
- creates any keys that are in your code but not yet in the ODB
- deletes any keys that are in the ODB but not your code
- updates the order of keys in the ODB to match your code

This will hopefully make it easier to automate ODB structure changes when you add/remove keys from a frontend.

The new feature is currently in the develop branch, and should be included in the next release.
    Reply  12 May 2021, Ben Smith, Bug Report, mhttpd WebServer ODBTree initialization 
> midas_hatfe_1  | Mongoose web server listening on http address "localhost:8080", passwords OFF, hostlist OFF
> midas_hatfe_1  | [mhttpd,ERROR] [mhttpd.cxx:19160:mongoose_listen,ERROR] Cannot mg_bind address "[::1]:8080"

It looks like mhttpd managed to bind to the IPv4 address (localhost), but not the IPv6 address (::1). If you don't need it, try setting "/Webserver/Enable IPv6" to false.
    Reply  09 Jul 2021, Ben Smith, Forum, Problem with python file reader 
Hi Francesco,

Can you send me an example file to look at please? Either attached to the elog or sent directly to bsmith@triumf.ca

Thanks,
Ben
    Reply  16 Mar 2022, Ben Smith, Bug Report, Python ODB watch 
> It seems that the second write operation "overlaps" the first one...

Hi Gennaro,

In principle the same issue can happen in C++ code, but is much less likely as the callbacks get executed  more quickly (partly due to C++/python in general, and partly because the python code does some extra work to make the interface more user-friendly). The C++ code at the end of this message adds a 100ms sleep to the callback and can result in output like this when you do quick edits of "Test[0-19]" in odbedit.

Element 1 is 0
Element 2 is 0
Element 3 is 0
Element 4 is 0
Element 5 is 0
Element 6 is 0
Element 7 is 1
Element 8 is 1
Element 9 is 1
etc...


I agree that this can be a really nasty source of bugs if you need to react to every change. I'll add a warning to the python docstrings, but I can't think of a way to make this more robust at the midas level - I think we'd need some sort of ODB "snapshot" system...









#include "midas.h"

void watch_fn(HNDLE hDB, HNDLE hKey, int index, void *info) {
  DWORD data = 0;
  INT buf_size = sizeof(data);
  db_get_data_index(hDB, hKey, &data, &buf_size, index, TID_DWORD);
  printf("Element %d is %u\n", index, data);
  ss_sleep(100);
}

int main() {
  HNDLE hDB, hClient, hTestKey;

  std::string host, expt;
  cm_get_environment(&host, &expt);
  cm_connect_experiment(host.c_str(), expt.c_str(), "test_odb", nullptr);
  cm_get_experiment_database(&hDB, &hClient);

  static const DWORD numValues = 20;
  DWORD data[numValues] = {};
  db_set_value(hDB, 0, "Test", data, sizeof(DWORD) * numValues, numValues, TID_DWORD);
  db_find_key(hDB, 0, "Test", &hTestKey);
  db_watch(hDB, hTestKey, watch_fn, nullptr);

  printf("Press any key to exit loop...\n");

  while (!ss_kbhit()) {
    cm_yield(1);
  }

  db_unwatch_all();
  db_delete_key(hDB, hTestKey, FALSE);
  cm_disconnect_experiment();

  return 0;
}
    Reply  17 May 2022, Ben Smith, Info, MIDAS switched to C++ 
>  - have you posted somewhere this guide about converting C frontends to C++?

See the instructions at:
https://daq00.triumf.ca/MidasWiki/index.php/Changelog#2019-06

>  - it was mentioned previously that there will be a 'tag the last "C" midas', which version is it?

>  - it means that even a simple example like odb_test.c cannot be compile anymore? Even when using g++?
> g++ -I $HOME/daq/packages/midas/include/ -L $HOME/daq/packages/midas/lib/ odb_test.c -l midas

Correct. Midas is built with C++, so names get mangled 
    Reply  17 May 2022, Ben Smith, Info, MIDAS switched to C++ 
>  - have you posted somewhere this guide about converting C frontends to C++?

There's documentation in the wiki at:
https://daq00.triumf.ca/MidasWiki/index.php/Changelog#2019-06

It includes a step-by-step guide of how to upgrade, what changes need to be made to frontends, and common issues that people had.
    Reply  14 Oct 2022, Ben Smith, Info, Allow onchange to refer to arbitrary js function 
> I would like to use a function defined in the <script> block of my custom page as an onchange callback.
>
> Is this a possibility?

Yes, this is already possible. An example was shown in the "modb" section of the custom page documentation, but not in the "Changing properties of controls dynamically" section. I've updated the wiki with an example.

https://daq00.triumf.ca/MidasWiki/index.php/Custom_Page#Changing_properties_of_controls_dynamically
    Reply  21 Apr 2023, Ben Smith, Forum, Setup Midas with Caen vx2740 - ask for help 
> I'm not able to find documentation what is purpose of the RPC? Could someone give any indicators how I can start debug this behavior? Or there is some documentation about the RPC?

The RPC system allows midas clients to issue commands to each other. In the case of the VX2740 code we use it so the midas webserver (mhttpd) can tell the frontend to perform some actions when a user clicks a button on a webpage.

I've been writing most of the code for the VX2740 for Darkside, so will contact you directly to help debug the issue.
ELOG V3.1.4-2e1708b5