xpainfo(3)

1xpainfo(3)                    SAORD Documentation                   xpainfo(3)
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NAME

6       XPAInfo: send short message to one or more XPA servers
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SYNOPSIS

9         #include <xpa.h>
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11         int XPAInfo(XPA xpa,
12                     char *template, char *paramlist, char *mode,
13                     char **names, char **messages, int n);
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DESCRIPTION

16       Send a short paramlist message to one or more XPA servers whose
17       class:name identifier matches the specified template.
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19       A template of the form "class1:name1" is sent to the XPA name server,
20       which returns a list of at most n matching XPA servers.  A connection
21       is established with each of these servers and the paramlist string is
22       passed to the server as the data transfer request is initiated. If an
23       XPA struct is passed to the call, then the persistent connections are
24       updated as described above. Otherwise, temporary connections are made
25       to the servers (which will be closed when the call completes).
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27       The XPAInfo() routine does not send data from a buf to the XPA servers.
28       Only the paramlist is sent.  The semantics of the paramlist is not
29       formalized, but at a minimum is should tell the server how to get more
30       information.  For example, it might contain the class:name of the XPA
31       access point from which the server (acting as a client) can obtain more
32       info using XPAGet.
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34       A string containing the class:name and ip:port of each server is
35       returned in the name array.  If a given server returned an error or the
36       server callback sends a message back to the client, then the message
37       will be stored in the associated element of the messages array.  The
38       returned message string will be of the form:
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40         XPA$ERROR   error-message (class:name ip:port)
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42       or
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44         XPA$MESSAGE message     (class:name ip:port)
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46       The return value will contain the actual number of servers that were
47       processed.  This value thus will hold the number of valid entries in
48       the names and messages arrays, and can be used to loop through these
49       arrays.  In names and/or messages is NULL, no information is passed
50       back in that array.
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52       The following keywords are recognized:
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54         key           value           default         explanation
55         ------        --------        --------        -----------
56         ack           true/false      true            if false, don't wait for ack from server
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58       When ack is false, XPAInfo() will not wait for an error return from the
59       XPA server. This means, in effect, that XPAInfo will send its paramlist
60       string to the XPA server and then exit: no information will be sent
61       from the server to the client. This UDP-like behavior is essential to
62       avoid race conditions in cases where XPA servers are sending info
63       messages to other servers. If two servers try to send each other an
64       info message at the same time and then wait for an ack, a race
65       condition will result and one or both will time out.
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67       Example:
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69         (void)XPAInfo(NULL, "IMAGE", "ds9 image", NULL, NULL, NULL, 0);
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NAME

SYNOPSIS

DESCRIPTION

SEE ALSO