>          I'm running a DAQ frontend and it works well if one single run is
> taken. If I try to take a second run right after, the run is performed but, when
> stopping it, I get the error messages below. Any hint?

Sure. I will read the error messages for you: note that they come in reverse time order - oldest message is at the bottom. I 
will reverse them in my reading:

> 11:42:23.994 2019/03/12 [cygnus_daq,ERROR] [midas.c:1951:,ERROR]
> cm_disconnect_experiment not called at end of program

your frontend has exited (this error message is printed by the atexit() code, so you did not crash but called exit(), 
somehow).

> 11:42:24.011 2019/03/12 [mhttpd,ERROR] [system.c:4661:recv_tcp2,ERROR]
> unexpected connection closure

mhttpd reports that the socket connection to your frontend has closed (because the frontend stopped, closing all it's 
sockets)

> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [system.c:4715:ss_recv_net_command,ERROR]
> error receiving network command header, see messages

mhttpd network code next layer reports this same error again

> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [midas.c:10821:rpc_client_call,ERROR]
> call to "cygnus_daq" on "localhost" RPC "rc_transition": error,
> ss_recv_net_command() status 411

mhttpd network code next layer reports this same error again, now we see that it was trying
to execute a "run start" (or "stop") RPC call to your frontend. But your frontend unexpectedly
shutdown (instead of replying to the RPC).

Next messages after that is mhttpd decided that your frontend is faulty (does not respond to RPC correctly) and tried to 
shut it down, but failed (cannot connect, etc). Last message is mhttpd cleaning up your frontend from ODB (because the 
frontend did not cleanup after itself - it did not call cm_disconnect_experiment(), per the very first error message).


So this is what we see from the midas messages - your frontend unexpectedly exited during the run transition - if as you 
say the run was stopping at the time, it would be in your end_of_run() function.

To debug this, I would do:

a) put some printf() statements in end_of_run() and see what they say during the crash
b) run the frontend inside the debugger, you may need to set a breakpoint on exit() or something like that.


Good luck,
K.O.





> 
> Thank you for your help,
>       Francesco
> 
> 
> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [midas.c:6022:cm_shutdown,ERROR] Killing
> and Deleting client 'cygnus_daq' pid 12472
> 
> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [midas.c:6019:cm_shutdown,ERROR] Cannot
> connect to client 'cygnus_daq' on host 'localhost', port 46341
> 
> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [midas.c:9539:rpc_client_connect,ERROR]
> cannot connect to host "localhost", port 46341: connect() returned -1, errno 111
> (Connection refused)
> 
> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [midas.c:10821:rpc_client_call,ERROR]
> call to "cygnus_daq" on "localhost" RPC "rc_transition": error,
> ss_recv_net_command() status 411
> 
> 11:42:24.012 2019/03/12 [mhttpd,ERROR] [system.c:4715:ss_recv_net_command,ERROR]
> error receiving network command header, see messages
> 
> 11:42:24.011 2019/03/12 [mhttpd,ERROR] [system.c:4661:recv_tcp2,ERROR]
> unexpected connection closure
> 
> 11:42:23.994 2019/03/12 [cygnus_daq,ERROR] [midas.c:1951:,ERROR]
> cm_disconnect_experiment not called at end of program