<HTML> <HEAD> <TITLE> The GGZ Gaming Zone Meta Server Project </TITLE> </HEAD> <BODY BGCOLOR="#334433" LINK="#ffffbb" ALINK="#ffffff" VLINK="#ffffbb"> <FONT COLOR="#ffffff" SIZE="4" FACE="arial,helvetica"> <B> <CENTER> <IMG SRC="pics/title.png"> </CENTER> <BR><BR> <IMG SRC="pics/about.png"><BR CLEAR="ALL"> This project has been founded to allow GGZ client programs to connect dynamically to GGZ servers, without knowing their version numbers or host name. Meta servers store lists of GGZ servers and pass them to the client on request. Furthermore, they store lists of peer servers to distribute changes automatically world-wide. <BR><BR> <IMG SRC="pics/clients.png"><BR CLEAR="ALL"> GGZ Core Clients, such like KGGZ or GGZ-Gtk, can use the meta servers to allow random connections, or to update their list of available hosts to connect to. This ensures that servers with too old or too new versions of ggzd are excluded automatically. The GGZ Telnet Wrapper (TelGGZ) uses this functionality for a similar task. <BR><BR> There is only one mode the clients use (query connections), but there are two different modes of doing this: Either they do a simple query using the URI notation, or a more complex one using the XML protocol. For a detailed format definition, see the specification below. The following could be an example of such a query: <BR><BR> <CENTER> <TABLE BORDER="0"> <TR> <TD BGCOLOR="#445544"> <FONT COLOR="#ffffff" SIZE="4" FACE="arial,helvetica"> Query Client -> Server:<BR> <FONT COLOR="#ffffbb"> query://ggz/connection/0.0.5pre<BR> </FONT> Result Server -> Client:<BR> <FONT COLOR="#ffffbb"> ggz://ggz.snafu.de:5688<BR> </FONT> </TD> </TR> </TABLE> </CENTER> <BR> In the issued query, 'ggz' is the class and 'connection' the subclass (named 'type') of the query, while '0.0.5pre' is the value. As one can see, other classes can be used as well, which ensures the usage of the meta server is not restricted to GGZ projects. The result simply returns an URI which is understood by the GGZ core clients. <BR><BR> Using the XML format is not so easy but instead it provides a higher flexibility. Let's repeat the example from above using XML notation: <BR><BR> <CENTER> <TABLE BORDER="0"> <TR> <TD BGCOLOR="#445544"> <FONT COLOR="#ffffff" SIZE="4" FACE="arial,helvetica"> Query Client -> Server:<BR> <FONT COLOR="#ffffbb"> <?xml version="1.0"?><BR> <query class="ggz" type="connection"><BR> 0.0.5pre<BR> </query><BR> </FONT> Result Server -> Client:<BR> <FONT COLOR="#ffffbb"> <?xml version="1.0"?><BR> <resultset referer="query"><BR> <result preference="100"><BR> <uri>ggz://jzaun.com:5688</uri><BR> <location>pennsylvania, us</location><BR> </result><BR> </resultset><BR> </FONT> </TD> </TR> </TABLE> </CENTER> <BR> It is now the client's task to build a list from this result set and either choose one host from it (preferably the one with the highest priority), or let the user select one. <BR><BR> <IMG SRC="pics/servers.png"><BR CLEAR="ALL"> The role of meta servers among each other is to distribte changes they received from an administrator. The distribution follows several rules, and happens automatically, while incorrect configuration of one server in such a web of trust should leave most parts of the web intact. <BR><BR> Each meta server stores a list of peer servers which are to be notified when changes occur, and each entry has the login data needed to authenticate on the peer host. Logically each meta server does also store a list of logins, consisting of username and password, of persons or servers which are allowed to issue updates. The following illustration gives you an overview about the whole update process. Note that updates can be additions, deletions and modifications. <BR><BR> <CENTER> <TABLE BORDER="0"> <TR> <TD BGCOLOR="#445544"> <FONT COLOR="#ffffff" SIZE="4" FACE="arial,helvetica"> A typical web of GGZ meta servers<BR> <IMG SRC="pics/web.png"> </TD> </TR> </TABLE> </CENTER> <BR> In the example above, the green boxes are players, and the ones with the black point in them are administrators, who have direct access to the meta server configuration. The red disks are GGZ servers, and the blue disks represent meta servers, with blue lines for the updates and dotted black lines for queries. <BR><BR> There exist currently two tools for administrators to update the meta servers: A perl script named metaconf.pl, and a Qt GUI named QMetaGUI. Both fulfil the task of avoiding typos and handling the XML embedding of the data. <BR><BR> <IMG SRC="pics/spec.png"><BR CLEAR="ALL"> The complete specification is available in text format. It does however only describe the protocol, not the local configuration file format, so other meta server implementations supporting the same protocol may be written. A HTML page containing this specification is available <A HREF="spec.html">here</A>. </B> <BR><BR> </FONT> </BODY> </HTML>
