xpaaccess(3)							SAORD Documentation						      xpaaccess(3)

NAME

       XPAAccess - return XPA access points matching template (XPA 2.1 and above)

SYNOPSIS

	 #include <xpa.h>

	 int XPAAccess(XPA xpa,
		       char *template, char *paramlist, char *mode,
		       char **names, char **messages, int n);

DESCRIPTION

       The XPAAccess routine returns the public access points that match the specified second argument template and have the specified access
       type.

       A template of the form "class1:name1" is sent to the XPA name server, which returns a list of at most n matching XPA servers.  A connection
       is established with each of these servers and the paramlist string is passed to the server as the data transfer request is initiated. If an
       XPA struct is passed to the call, then the persistent connections are updated as described above. Otherwise, temporary connections are made
       to the servers (which will be closed when the call completes).

       The XPAAccess() routine retrieves names from at most n XPA servers that match the specified template and that were checked for access using
       the specified mode.  The return string contains both the class:name and ip:port.  If a given server returned an error or the server call-
       back sends a message back to the client, then the message will be stored in the associated element of the messages array.  NB: if speci-
       fied, the name and messages arrays must be of size n or greater.

       The returned message string will be of the form:

	 XPA$ERROR error-message (class:name ip:port)

       Note that names of matching registered access points are always returned but may not be valid; it is not sufficient to assume that the
       returned number of access points is the number of valid access points.  Rather, it is essential to check the messages array for error mes-
       sages.  Any string in the messages array is an error message and indicated that the associated access point is not available.

       For example, assume that a server registers a number of access points but delays entering its event loop. If a call to XPAAccess() is made
       before the event loop is entered, the call will timeout (after waiting for the long timeout period) and return an error of the form:

	 XPA$ERROR: timeout waiting for server authentication (XPA:xpa1)

       The error means that the XPA access point has been registered but is not yet available (because events are not being processed). When the
       server finally enters its event loop, subsequent calls to XPAAccess() will return successfully.

       NB: This routine only works with XPA servers built with XPA 2.1.x and later.  Servers with older versions of XPA will return the error mes-
       sage:

	 XPA$ERROR invalid xpa command in initialization string

       If you get this error message, then the old server actually is ready for access, since it got to the point of fielding the query! The
       xpaaccess program, for example, ignores this message in order to work properly with older servers.

       The third argument for XPAAccess() is the type of access and can be any combination of:

	 type	       explanation
	 ------        -----------
	 g	       xpaget calls can be made on this access point
	 s	       xpaset calls can be made on this access point
	 i	       xpainfo calls can be made on this access point

       The mode string argument is of the form: "key1=value1,key2=value2,..."  The following keywords are recognized:

	 key	       value	       default	       explanation
	 ------        --------        --------        -----------
	 ack	       true/false      true	       if false, don't wait for ack from server (after callback completes)

       The ack keyword is not very useful, since the server completes the callback in order to return the data anyway.	It is here for completion
       (and perhaps for future usefulness).

SEE ALSO

       See xpa(7) for a list of XPA help pages

version 2.1.14							   June 7, 2012 						      xpaaccess(3)