Applications over Freenet: a Decentralized, Anonymous Gaming API?
In this article, I'll tell you how to write a simple, generic gaming API on top of Freenet using the shiniest new Freenet APIs and design patterns. Why write games over Freenet? Well, you can play without a central server, without having to worry about attackers falsifying moves and without knowing who you're playing against! Some people question the usefulness of these features. The real reason is it's more fun to implement than a relational database, and I'm not exactly getting paid for this. But wait, is Freenet real time? Is it fast enough to play a satisfying game of anonymous Quake on top of it? No, it's about as fast as e-mail or a heavily loaded web server, depending on the weather. Remember the part about us being crazy and not getting paid.
There are lots of ways to interface with your node; I won't cover them all here. Anyone who can use the Java Servlet API and one of the client APIs can write a new interface that runs inside the node. The Freenet HTTP Proxy (FProxy) is written this way, for instance. The interface I prefer for talking to my node is XML-RPC. There are XML-RPC libraries in at least 21 languages and some other things that may or may not be languages; I couldn't tell.
There are four different APIs exposed via XML-RPC in the Freenet reference implementation. The Util API supplies utility methods for determining the version of your node and other sundry items that don't concern us. The Simple API provides a one-line method call to insert and request files but is not designed to handle big files. The Chunked API allows for chunked retrieval of large files. The Streaming API allows for efficient streaming retrieval of data. I'm going to cover only the Simple API, as it is completely sufficient for our purposes.
Even though XML-RPC client can be written in 21 languages, I like Java best, so all of the examples will be in Java. If you're writing your code in Java, the power of interfaces means you don't have to think about XML-RPC at all. If you want to call the API directly (for instance, if you're writing code for a plugin that will run inside the node), then you instantiate a LocalSimpleClient. If you want to call the API via XML-RPC (for a standalone client), you then instantiate a RemoteSimpleClient. Either way, the rest of your code looks the same.
Using a LocalSimpleClient involves some parameter setting that isn't very interesting, and useful only if you're developing a node plugin, so I'll just cover RemoteSimpleClient. You instantiate a RemoteSimpleClient with a URL pointing it to the XML-RPC server. If your XML-RPC server is running on the default port as of the 0.3.8.1 Freenet release, your code should look like this:
SimpleClient client = new RemoteSimpleClient("http://localhost:6690");
Freenet is essentially a distributed hard drive with various optimizations and security features. As such, the Simple API looks like a Hashtable with a mysterious extra parameter, HTL. This parameter is the "Hops to Live" or, in other words, how many nodes you want to search before you give up. This number can be tricky to guess. The larger it is, the longer you have to wait for it to timeout if a file isn't in the network. However, the smaller it is, the greater the chance is that you won't find a file when it is indeed in the network. I recommend you set it high (say 100) and learn Zen-like patience.
Apart from guessing an HTL parameter, requesting and inserting files using the Simple API is simple and obvious by looking at the interface, but it's not anything you couldn't do from the command line. For a more exciting project, we must implement our gaming API.
A gaming API needs to: 1) track who wants to play, who is playing and who is watching, etc.; 2) match prospective players to start games; 3) route moves to players of a game; 4) provide an engine to check for validity of moves, states and score players; 5) provide a database of wins, losses and scores; and 6) a provide rating/ranking engine.
I'm supposed to be writing about Freenet more than gaming engines, so I'll only cover the first three needs at the moment. Number four should be done by a dedicated and modular piece of software so that different game engines can be plugged into the generic architecture. Items four through six contain issues of reputation and trusted relationships that should keep any self-respecting P2P programmer up at night pondering cheating, lying and control of information resources.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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|SUSE LLC's SUSE Manager||Jul 21, 2016|
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- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Parsing an RSS News Feed with a Bash Script
- Doing for User Space What We Did for Kernel Space
- Google's SwiftShader Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide