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104 lines
4.2 KiB
104 lines
4.2 KiB
The code here demonstrates the use of INDI, an Instrument-Neutral Device
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Interface protocol. See http://www.clearskyinstitute.com/INDI/INDI.pdf.
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Architecture:
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Typical INDI Client / Server / Driver / Device connectivity:
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INDI Client 1 ----| |---- INDI Driver A ---- Dev X
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INDI Client 2 ----| |---- INDI Driver B ---- Dev Y
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... |--- indiserver ---| |-- Dev Z
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INDI Client n ----| |---- INDI Driver C ---- Dev T
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Client INET Server UNIX Driver Hardware
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processes sockets process pipes processes devices
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Indiserver is the public network access point where one or more INDI Clients
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may contact one or more INDI Drivers. Indiserver launches each driver
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process and arranges for it to receive the INDI protocol from Clients on
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its stdin and expects to find commands destined for Clients on the
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driver's stdout. Anything arriving from a driver process' stderr is copied
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to indiserver's stderr.
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Indiserver only provides convenient port, fork and data steering services.
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If desired, a Client may run and connect to INDI Drivers directly.
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Construction:
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An INDI driver typically consists of one .c file, eg, mydriver.c, which
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#includes indiapi.h to access the reference API declarations. It is
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compiled then linked with indidrivermain.o, eventloop.o and liblilxml.a to
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form an INDI process. These supporting files contain the implementation of
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the INDI Driver API and need not be changed in any way. Note that
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evenloop.[ch] provide a nice callback facility independent of INDI which
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may be used in other projects if desired.
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The driver implementation, again in our example mydriver.c, does not
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contain a main() but is expected to operate as an event-driver program.
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The driver must implement each ISxxx() function but never call them. The
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IS() functions are called by the reference implementation main() as messages
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arrive from Clients. Within each IS function the driver performs the
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desired tasks then may report back to the Client by calling the IDxxx()
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functions.
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The reference API provides IE() functions to allow the driver to add its
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own callback functions if desired. The driver can arrange for functions to
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be called when reading a file descriptor will not block; when a time
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interval has expired; or when there is no other client traffic in progress.
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The sample indiserver is a stand alone process that may be used to run one
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or more INDI-compliant drivers. It takes the names of each driver process
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to run in its command line args.
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To build indiserver type 'make indiserver';
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to build all the sample drivers type 'make drivers';
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to run the sample server with all drivers type 'make run'.
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Killing indiserver will also kill all the drivers it started.
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Secure remote operation:
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Suppose we want to run indiserver and its clients on a remote machine, r,
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and connect them to our favorite INDI client, XEphem, running on the
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local machine.
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From the local machine log onto the remote machine, r, by typing:
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ssh2 -L 7624:s:7624 r
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after logging in, run indiserver on the remote machine:
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make run
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Back on the local machine, start XEphem, then open Views -> Sky View ->
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Telescope -> INDI panel. XEphem will connect to the remote INDI server
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securely and automatically begin running. Sweet.
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Testing:
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A low-level way to test the socket, forking and data steering abilities of
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indiserver is to use the 'hose' command from the netpipes collection
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(http://web.purplefrog.com/~thoth/netpipes/netpipes.html):
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1. start indiserver using UNIX' cat program as the only INDI "device":
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% indiserver cat &
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2. use hose to connect to the "cat" device driver which just copies back:
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% hose localhost 7624 --slave
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hello world
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hello world
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more stuff
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more stuff
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! For RCS Only -- Do Not Edit
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! @(#) $RCSfile$ $Date$ $Revision$ $Name: $
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