DALI User Manual: Server Setup

Overview

The DALI server executable is located in the /bin/ sub-directory of the DALI install directory. There are a number of options which specify the configuration of the DALI server. These options can either be specified on the command line when the DALI server is run, or added to a simple key=value INI file which is checked by the server when it starts.

By default the INI file is called dali.ini and it is located in the DALI install directory. Here is an example dali.ini file:

port=8444
passwordfile=/usr/local/dali/etc/passwd

These options could be specified on the command line when running the DALI server instead, as in this example:

$ dalid -port 8444 -passwordfile /usr/local/dali/etc/passwd

Board Locking

Data acquisition boards are not designed to support multiple programs interacting with them at the same time. DALI will malfunction, or disrupt other programs if they try to use a board while DALI is servicing a request for the same board. If possible, all software should use DALI to communicate with the data acquisition hardware rather than programming the boards directly.

However, if you must communicate with the DAQ hardware independant of DALI a feature called Board Locking is supported which allows you to sychronize your operations with DALI to ensure that only one program is talking to the board at a time.

The lockboards directive which is documented below enables this feature. When enabled, DALI will lock the board automatically before each board access, and unlock it when done. Any 3rd party program which will sychronize access to the board with DALI must do the same. When a "lock" is in use, the other program should wait until the "lock" is released before accessing the board.

On Linux and QNX, DALI will create lock files in the boards directory. The lock file for a board will be the name of the board followed by ".lock". The following code should be added to any 3rd party program which will use these lock files to synchronize with the DALI server.

	char *lockfile = "/usr/local/dali/boards/myboard.lock";
	int fd = open(lockfile, O_RDONLY|O_CREAT, S_IREAD);
	flock(fd, LOCK_EX);
	// Your DAQ programming code goes here
	flock(fd, LOCK_UN);
	close(fd);

On Windows, Named Mutexes are used instead. For example, a mutex named DALI_IPC_MUTEX_MYBOARD is created by the DALI server if you have a board named myboard. The following code should be added to any 3rd party program which will use these lock files to synchronize with the DALI server.

	HANDLE hdl = CreateMutex(NULL, FALSE, "DALI_IPC_MUTEX_MYBOARD");
	WaitForSingleObject(hdl, INFINIE);
	// Your DAQ programming code goes here
	ReleaseMutex(hdl);
	CloseHandle(hdl);

Note that board locking has a serious impact on DALI A/D performance. Since DALI can no longer assume it has full control of a board, it must repeat A/D mode setup before each A/D sample.

Server Configuration Directives