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diff --git a/xpa/doc/xpans.html b/xpa/doc/xpans.html deleted file mode 100644 index a0aebb2..0000000 --- a/xpa/doc/xpans.html +++ /dev/null @@ -1,212 +0,0 @@ -<!-- =defdoc xpans xpans 1 --> -<HTML> -<HEAD> -<TITLE>The XPA Name Server (xpans)</TITLE> -</HEAD> -<BODY> - -<!-- =section xpans NAME --> -<H2><A NAME="xpans">xpans: the XPA Name Server</A></H2> - -<!-- =section xpans SYNOPSIS --> -<H2>Summary</H2> -<PRE> - xpans [-h] [-e] [-k sec] [-p port] [-l log] [-s security log] [-P n] -</PRE> - -<!-- =section xpans OPTIONS --> -<P> -<PRE> - -h print help message - -e exit when there are no more XPA connections - -k send keepalive messages every n sec - -l log data base entries to specified file - -p listen for connections on specified port - -s log security info for each connection to specified file - -P accept proxy requests (P=1) using separate thread (P=2) - --version display version and exit -</PRE> - -<!-- =section xpans DESCRIPTION --> -<P> -The xpans name server is an XPA-enabled program that is used to -manage the names and ports of XPA access points. It is started -automatically when an XPA access point is registered. You can access -the name server using xpaget to get a list of registered access points. -<P> -The <EM>xpans</EM> name server provides a crucial link between XPA -clients and servers. When an XPA server defines an access point using -XPANew(), XPACmdNew(), or XPAInfoNew(), the name of the access point -is registered in the name service, along with connection information. -The name server then matches class:name templates passed to it by XPA -clients with these registered entries, so that the clients can -communicate with the appropriate servers. - -<P> -The socket connection between an XPA-enabled program and -<EM>xpans</EM> is kept open until the former exits (or explicitly -closes the connection). Apparently, some Internet equipment (e.g. DSL -modems) can cause such a connection to time-out after a period of -inactivity. To prevent this from happening, you can use the <EM>-k -[sec]</EM> switch to send a short keep-alive message to each open -connection after the specified time delay. (Note that this -application level use of keep-alive is necessary only if you are -serving XPA-enabled clients over the Internet and have to deal with -long-term connections involving DSL or similar equipment. XPA uses -the ordinary socket-level keep-alive, which works for all other cases.) -<B>NB (12/2/2009): Out-of-band (URG) TCP data, used by xpans -keep-alive, is changed by some Cisco routers into in-band data. -Encountering such a router will break the keep-alive function and may -break your XPA server as well. Proceed with caution!</B> - -<P> -The <EM>xpans</EM> program will be started automatically (assuming it -can be found in the user's path) when the first XPA access point is -registered. It therefore need not be started explicitly. However, -when started automatically, the <EM>-e</EM> switch is used, so that -the name server will exit when there are no more XPA access points -registered. If you wish to keep the name server running continually, -simply start it manually without the <EM>-e</EM> switch. - -<P> -The name server will keep a log of registered access points if the -<EM>-l [log]</EM> switch is used on the command line (this is the -case for automatic start-up). The log contains enough name and connection -information to allow you to re-register all XPA access points in case -the name server process is terminated prematurely. For example, after -the ds9 access point is registered,the log will contain the entry: -<PRE> - add 838e2f67:1863 ds9 ds9 gs eric -</PRE> -If <EM>xpans</EM> is terminated but ds9 still is running, you -can re-register both access points for the ds9 process by running: -<PRE> - xpaset -p 838e2f67:1863 -nsconnect -</PRE> -Notice that the ip:port specifier is used with <EM>xpaset</EM> to bypass -the need for contacting the name server (which does not have the name -registered yet!) - -<P> -The name server will keep a log of security information if the <EM>-s -[security log]</EM> switch is used on the command line. For each -accepted connection, (including connections via the <EM>xpaget</EM> -command), information will be logged about the host issuing the -command and the parameters passed into the program. This is most -useful when <EM>xpans</EM> is accepting connections from untrusted -machines. - -<P> -When an XPA access point is removed by a server using <EM>XPAFree()</EM>, -the access information is removed from the name server. If an -XPA-enabled process is terminated, all names registered by that process -will be removed automatically. The log file is always updated to -reflect the currently registered access points. - -<P> -The name server itself has an XPA access point names <EM>xpans</EM> -registered through which you can find out information about currently -registered access points (assuming you have access to the name server; -see <A HREF="./acl.html">XPA Access Control</A> for more information). -For each registered access point, the following information is returned: -<PRE> - class # class of the access point - name # name of the access point - access # allowed access (g=xpaget,s=xpaset,i=xpainfo) - id # socket access method (host:port for inet, file for local/unix) - user # user name of access point owner -</PRE> - -<P> -For example, to display all currently registered access points, simply execute: -<PRE> - xpaget xpans -</PRE> -Continuing the example of ds9 above, this will return: -<PRE> - DS9 ds9 gs 838e2f67:1863 eric -</PRE> -If the same program has been started with different XPA access names, -you can look up only names matching a specified template. For example, -assume that ds9 has been started up using: -<PRE> - ds9 & - ds9 -title ds9-1-eric & - ds9 -title ds9-2-eric & -</PRE> -To lookup all ds9 access points which end in ".eric" and which can -be accessed using <EM>xpaset</EM>, use: -<PRE> - xpaget xpans "DS9:*.eric" "s" "*" -</PRE> -This will return: -<PRE> - DS9 ds9-2-eric gs 838e29d3:42102 eric - DS9 ds9-1-eric gs 838e29d3:42105 eric -</PRE> -The third argument "*" requests all access points from all users. -You also can specify a specific user name and only access points -registered by that user will be returned. - -<P> -The name server uses the <EM>XPA_METHOD</EM> environment variable -to determine whether it should listen for requests on INET or LOCAL -sockets. Since XPA access points also use this environment variable, -the choice of socket method will be consistent. Note that, when INET -sockets are used, a local server can be accessed from remote machines -if the <EM>XPA_NSINET</EM> environment variable is set to point to -the local machine. See -<A HREF="./env.html">XPA Environment Variables</A> -for more information. - -<P> -An experimental feature of xpans is its ability to act as a proxy to -XPA servers behind firewalls that want to communicate with external -processes. The basic idea is the following: an XPA server (call it -"foo") on host1, possibly behind a firewall, makes a remote connection -to a proxy-enabled xpans program on host2 (specifying host2's XPA method). -For example: -<PRE> - xpaset -p foo -remote 'host2:28571' + -proxy # on host1 -</PRE> -When this is done, host2 can use xpaset, xpaget, and xpainfo calls to -communicate with the XPA server foo. All command communication is -performed via the xpans socket connection between foo on host1 and -xpans on host2 (which was initiated by foo from inside the firewall). -Data communication is similarly performed using a socket connection -initiated on host1 (usually with a port value two greater than the -port value of the main xpans socket connection). An xpaset or xpaget -call on host2 contacts xpans, which performs an XPASet() or XPAGet() -call to foo, passing commands and data back and forth between the two -programs. - -<P> -By default, proxy connections are not allowed by xpans. If the -P switch is -specified with a value of 1, proxy connection are allowed, but all proxy -communication is performed in the same thread as xpans processing. If -a value of 2 is specified, the proxy processing is performed in a -separate thread (assuming pthreads are supported on your system). -Because xpa callback processing of any type can take a long time and -therefore can interfere with normal xpans processing, threaded proxy -connections (-P 2) are recommended. When using proxy connections, it -might also be useful to set the XPA_IOCALLSXPA environment variable, so -that multiple proxy requests can be handled at the same time, instead of -serially. - -<P> -Note that this proxy interface to xpans is experimental. It is used -to provide remote data analysis capabilities on the Chandra-Ed system -using ds9. (See http://chandra-ed.cfa.harvard.edu and -http://hea-www.harvard.edu/saord/ds9 for more details). As always, please -contact us if you have problems or questions. - -<!-- =section xpans SEE ALSO --> -<!-- =text See xpa(n) for a list of XPA help pages --> -<!-- =stop --> - -<P> -<A HREF="./help.html">Go to XPA Help Index</A> - -<H5>Last updated: January 24, 2005</H5> -</BODY> -</HTML> |