| 1 | libindi v0.8 |
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| 2 | ============ |
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| 3 | |
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| 4 | The code here demonstrates the use of INDI, an Instrument-Neutral Device |
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| 5 | Interface protocol. See http://www.clearskyinstitute.com/INDI/INDI.pdf. |
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| 6 | |
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| 7 | Architecture: |
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| 8 | |
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| 9 | Typical INDI Client / Server / Driver / Device connectivity: |
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| 10 | |
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| 11 | |
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| 12 | INDI Client 1 ----| |---- INDI Driver A ---- Dev X |
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| 13 | | | |
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| 14 | INDI Client 2 ----| |---- INDI Driver B ---- Dev Y |
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| 15 | | | | |
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| 16 | ... |--- indiserver ---| |-- Dev Z |
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| 17 | | | |
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| 18 | | | |
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| 19 | INDI Client n ----| |---- INDI Driver C ---- Dev T |
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| 20 | |
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| 21 | |
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| 22 | Client INET Server UNIX Driver Hardware |
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| 23 | processes sockets process pipes processes devices |
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| 24 | |
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| 25 | |
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| 26 | |
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| 27 | Indiserver is the public network access point where one or more INDI Clients |
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| 28 | may contact one or more INDI Drivers. Indiserver launches each driver |
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| 29 | process and arranges for it to receive the INDI protocol from Clients on |
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| 30 | its stdin and expects to find commands destined for Clients on the |
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| 31 | driver's stdout. Anything arriving from a driver process' stderr is copied |
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| 32 | to indiserver's stderr. |
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| 33 | |
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| 34 | Indiserver only provides convenient port, fork and data steering services. |
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| 35 | If desired, a Client may run and connect to INDI Drivers directly. |
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| 36 | |
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| 37 | Construction: |
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| 38 | |
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| 39 | An INDI driver typically consists of one .c file, eg, mydriver.c, which |
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| 40 | #includes indiapi.h to access the reference API declarations. It is |
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| 41 | compiled then linked with indidrivermain.o, eventloop.o and liblilxml.a to |
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| 42 | form an INDI process. These supporting files contain the implementation of |
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| 43 | the INDI Driver API and need not be changed in any way. Note that |
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| 44 | evenloop.[ch] provide a nice callback facility independent of INDI which |
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| 45 | may be used in other projects if desired. |
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| 46 | |
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| 47 | The driver implementation, again in our example mydriver.c, does not |
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| 48 | contain a main() but is expected to operate as an event-driver program. |
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| 49 | The driver must implement each ISxxx() function but never call them. The |
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| 50 | IS() functions are called by the reference implementation main() as messages |
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| 51 | arrive from Clients. Within each IS function the driver performs the |
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| 52 | desired tasks then may report back to the Client by calling the IDxxx() |
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| 53 | functions. |
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| 54 | |
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| 55 | The reference API provides IE() functions to allow the driver to add its |
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| 56 | own callback functions if desired. The driver can arrange for functions to |
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| 57 | be called when reading a file descriptor will not block; when a time |
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| 58 | interval has expired; or when there is no other client traffic in progress. |
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| 59 | |
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| 60 | The sample indiserver is a stand alone process that may be used to run one |
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| 61 | or more INDI-compliant drivers. It takes the names of each driver process |
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| 62 | to run in its command line args. |
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| 63 | |
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| 64 | To build indiserver type 'make indiserver'; |
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| 65 | to build all the sample drivers type 'make drivers'; |
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| 66 | to run the sample server with all drivers type 'make run'. |
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| 67 | Killing indiserver will also kill all the drivers it started. |
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| 68 | |
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| 69 | Secure remote operation: |
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| 70 | |
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| 71 | Suppose we want to run indiserver and its clients on a remote machine, r, |
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| 72 | and connect them to our favorite INDI client, XEphem, running on the |
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| 73 | local machine. |
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| 74 | |
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| 75 | From the local machine log onto the remote machine, r, by typing: |
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| 76 | |
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| 77 | ssh2 -L 7624:s:7624 r |
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| 78 | |
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| 79 | after logging in, run indiserver on the remote machine: |
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| 80 | |
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| 81 | make run |
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| 82 | |
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| 83 | Back on the local machine, start XEphem, then open Views -> Sky View -> |
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| 84 | Telescope -> INDI panel. XEphem will connect to the remote INDI server |
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| 85 | securely and automatically begin running. Sweet. |
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| 86 | |
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| 87 | Testing: |
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| 88 | |
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| 89 | A low-level way to test the socket, forking and data steering abilities of |
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| 90 | indiserver is to use the 'hose' command from the netpipes collection |
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| 91 | (http://web.purplefrog.com/~thoth/netpipes/netpipes.html): |
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| 92 | |
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| 93 | 1. start indiserver using UNIX' cat program as the only INDI "device": |
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| 94 | |
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| 95 | % indiserver cat & |
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| 96 | |
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| 97 | 2. use hose to connect to the "cat" device driver which just copies back: |
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| 98 | |
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| 99 | % hose localhost 7624 --slave |
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| 100 | hello world |
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| 101 | hello world |
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| 102 | more stuff |
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| 103 | more stuff |
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| 104 | |
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| 105 | |
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