XPAAccess - return XPA access points matching template (XPA 2.1 and
int XPAAccess(XPA xpa,
char *template, char *paramlist, char *mode,
char **names, char **messages, int n);
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 callback
sends a message back to the client, then the message will be stored in
the associated element of the messages array. NB: if specified, the
name and messages arrays must be of size n or greater.
The returned message string will be of the form:
XPA$ERROR error\-message (class:name ip:port)
Note that names of matching registered access points are always
returned but may not be valid; it is not sufficient to assume that the
returned number of access points is the number of valid access points.
Rather, it is essential to check the messages array for error messages.
Any string in the messages array is an error message and indicated that
the associated access point is not available.
For example, assume that a server registers a number of access points
but delays entering its event loop. If a call to XPAAccess() is made
before the event loop is entered, the call will timeout (after waiting
for the long timeout period) and return an error of the form:
XPA$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
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
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 xpa(7) for a list of XPA help pages