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Building the Server

Software Experiments

Software Experiments

New Experimental Software

Here is where I will discuss some software experiments oriented towards demonstrating possible applications of RPOW. These are in a little rougher condition than the rest of the RPOW package but developers may find them useful as samples and examples of how RPOW can be used.

Python and Perl

RPOW can now be used with scripting languages such as Python and Perl. This allows easy integration of RPOW into programs written in those languages.

This integration is made possible with the help of SWIG. SWIG takes a C or C++ language library, such as RPOW, and allows it to be called from a variety of scripting languages. It supports not only Python and Perl, but also Ruby, Java, PHP, Ocaml, Guile and others. Only Perl and Python are explicitly supported in the RPOW Makefile, but it would be straightforward to add support for the other languages.

To use these features, download SWIG, build and install it. Make sure that the installed swig program is on your command path. You can now build the Python and Perl interfaces for RPOW, by using the appropriate make commmand.

SWIG has been tested with RPOW on Mac OS X and Linux systems, and make targets exist for these, for both Python and Perl: make swig_python_osx, make swig_perl_osx, make swig_python_linux, and make swig_perl_linux. Give whichever command is appropriate for your machine architecture and the language you want to support. The RPOW Makefile includes explicit path names for the development directories associated with these languages. These path names may differ for different versions and installation modes of the languages, so it may be necessary to change them slightly for your system.

No documentation yet exists for the full exported API available from the scripting languages. The rpow.i file is the input to SWIG and describes all of the functions that are available. The examples below will illustrate some of the functionality.

Python examples

$ python
Python 2.3 (#1, Sep 13 2003, 00:49:11) 
[GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import rpow
>>> rp1 = rpow.gen(20)
>>> rp1.value
>>> str1 = rpow.to_string(rp1)
>>> str1
>>> rp2 = rpow.from_string(str1)
>>> rp2.value
>>> rp3 =
>>> rp3.value
>>> rpow.to_string(rp3)
>>> rpow.countvals(20)
>>> rpow.countvals(20)
>>> rp4 = rpow.load(20)
>>> rpow.to_string(rp4)
>>> rpow.countvals(20)

Perl examples

#! /usr/bin/perl

use rpow;

$val = $ARGV[0];
$rp1 = rpowc::gen($val);
print rpowc::to_string($rp1), "\n";

#! /usr/bin/perl

use rpow;

# receive an rpow on stdin, exchange it, store it and return its value
$strin = <>;
if (!defined($strin)) {
        print "Bad string\n";
        exit (0);
$rp1 = rpowc::from_string($strin);
if (!defined($rp1)) {
        print "Bad string\n";
        exit (0);
$rp2 = rpowc::exchange($rp1);
if (!defined($rp2)) {
        print "Exchange failed\n";
        exit (0);
$val = rpowc::rpow_value_get($rp2);
print "Succeded with value $val\n";
exit ($val);

RPOW enabled BitTorrent

One of the most revolutionary programs to come out of the P2P (peer to peer) community is Bram Cohen's BitTorrent. BitTorrent has been spectacularly successful at using the power of peer oriented networking to accelerate the download of large files. By spreading around the network traffic load, even files with many people trying to download them can be handled efficiently, as each person uploads as well as downloads. This sharing mechanism means that the traffic capacity of the network scales as more users are added.

One of the cleverest features of BitTorrent is its "tit for tat" mechanism to encourage people to participate as uploaders rather than as "leeching" downloaders. Each node chooses who it will upload to based on a simple algorithm that gives greater priority to the nodes that are downloading generously to it. This policy encourages people to upload so that they can improve their download speeds. It is decentralized and efficient at accomplishing its task, and this is in large part why BitTorrent has been so successful

However, one area could seemingly use some improvement. Once someone has finished downloading their data, they no longer have any motivation to stay connected to the network and participate by uploading. Doing so would benefit the network and the peers, but there is no direct reward to the person who does so. An informal system of etiquette has arisen among BitTorrent users, with the rule being that you should leave your node connected until your upload total is at least as big as your download total. But there is no mechanism within BitTorrent to encourage people to follow this rule.

RPOW tokens could provide such a mechanism. Imagine a version of BitTorrent where nodes that have completed their downloading (called "seeders") could earn RPOWs by continuing to upload. And what could they do with those RPOWs? Imagine further that this version of BitTorrent allowed nodes to send RPOWs in order to get higher priority from other nodes which are downloading. Just such an experimental, RPOW-enhanced version of BitTorrent is now available for download.

This program, BTRP (BitTorrent RPOW), is a patched version of the command line BitTorrent program, which is written in Python. It uses the SWIG Python interface described above to add features to BitTorrent to create, send, receive and exchange RPOWs. RPOW enabled nodes recognize each other and exchange information about what size RPOW they would like to receive per megabyte of uploaded traffic. If the request is acceptable, each node will send an RPOW of the appropriate size periodically. As long as a node is up to date on the RPOWs it has sent, it is given priority for uploads. BitTorrent nodes have a limited number of upload slots, and up to date RPOW nodes get priority for those slots.

This simple mechanism provides motivation for nodes to act as seeders and continue to upload in order to earn RPOWs, and rewards such nodes by allowing them to get priority on subsequent downloads. In this way nodes which act as seeders one day can be rewarded the next day when they download an entirely different file from a different group of peers.

For those who want to experiment with this capability, the download is available from the link above. The details are in the README.RPOW file. BTRP will work compatibly with ordinary BT nodes when taking to them, and the special RPOW features will only be enabled when talking to other BTRP nodes. So for test purposes you will need to set up a private BitTorrent download network which is running multiple BTRP nodes in order to see the new features in operation. What you should see, if you have a mix of BTRP and ordinary BT nodes, is that the BTRP nodes pay each other RPOWs and acquire priority for downloads in that way.

Keep in mind that this is a simple experiment at this time. I don't intend to deploy this on a large scale, and it's not even clear that BitTorrent is the best target for an RPOW enhanced P2P file sharing program. Indeed, there are a number of issues which would have to be addressed before such a deployment, including questions of whether users could cheat and acquire RPOWs without downloading data. There could conceivably be negative effects on the efficiency of the BitTorrent network if people who had earned RPOWs could get higher priority than other users who were uploading freely, thereby failing to reward uploading. On the other hand, those uploaders would be motivated to continue in order to acquire RPOWs. The net effect is hard to predict.

These questions will all benefit from further study, but the BTRP program will hopefully serve as an example of how RPOW can be integrated into existing programs. I hope to provide further examples in the future, such as a version of spamassassin enhanced to receive RPOWs in the message header as an indication that mail is not spam.