Command Protocol

For processes located at different machines a simple protocol over TCP/IP was developed. We recognized the idea of CORBA but found that in our case TCP/IP suits well.

Table 6 lists messages passing from the daq_ctrl process to the daq_main process and backward. Each message starts with a message ID followed by variable number of arguments. The number and meaning of variables are specified in the Table 7.

Table 6: Messages

MESSAGE	ID	DESCRIPTION
daq_ctrl $\rightarrow$ daq_main
STARTUP	1	initiate the system
SHUTDOWN	2	terminate the system
SOR	3	start of run
EOR	4	end of run
POR	5	pause of run
COR	6	continuation of run
RST	19	restart process
KILL	20	kill process
FEINIT	21	initialize FE electronics
daq_main $\rightarrow$ daq_ctrl
EMPTY	0	empty command - do nothing, used as acknowledgment for a previous command
EORN	7	EOR caused by events number limit
CHST	8	change of state
NEVT	9	informs about the number of recorded events or about the number of collected events if recording is switched off; contains also information about process states
MOND	10	connection to the monitor daemon established
REC	11	recording statistics
QTI	12	information about percentage of tape usage
QTW	13	warning: tape size can be exceeded soon
EOT	14	end of tape reached
UMNT	15	unmount tape
MNT	16	mount tape
PEOF	17	pseudo eof reached - open new file
RPS	18	pause of recording

Table 7: Message arguments.

Message	Arg size	Description
	(bytes)
EMPTY	0	no
STARTUP	1	processes to be activated
	1	run type
	1	recording type
	1	readout electronics architecture
	8	tape VID
SHUTDOWN	0	no
SOR	4	run number
	4	maximum number of events per run
EOR	4	run number
POR	4	run number
COR	4	run number
FEINIT	0	no
RST	1	EP
KILL	1	EP
EORN	4	run number
CHST	1	EP which changed state
	1	new state
NEVT	4	number of events
	3	EP states (daq_fe, daq_rec, daq_mon)
MOND	0	no
daq_rec	4	number of written records (events)
	4	number of written Mbytes
	4	number of written bytes ($<$1Mb)
	4	number of written files
QTI	4	percentage of tape usage
QTW	0	no
PEOF	4	number of written records (events)
	4	number of written Mbytes
	4	number of written bytes ($<$1Mb)
	4	number of written files
EOT	0	no
UMNT	0	no
MNT	8	tape VID
RPS	x	undefined yet