libtorrent Examples

Author: Arvid Norberg, arvid@rasterbar.com

Table of contents

examples

Except for the example programs in this manual, there's also a bigger example of a (little bit) more complete client, client_test. There are separate instructions for how to use it here if you'd like to try it. Note that building client_test also requires boost.regex and boost.program_options library.

dump_torrent

This is an example of a program that will take a torrent-file as a parameter and print information about it to std out:

#include <iostream>
#include <fstream>
#include <iterator>
#include <iomanip>

#include "libtorrent/entry.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/torrent_info.hpp"
#include "libtorrent/lazy_entry.hpp"
#include <boost/filesystem/operations.hpp>


int main(int argc, char* argv[])
{
        using namespace libtorrent;
        using namespace boost::filesystem;

        if (argc != 2)
        {
                std::cerr << "usage: dump_torrent torrent-file\n";
                return 1;
        }
#if BOOST_VERSION < 103400
        boost::filesystem::path::default_name_check(boost::filesystem::no_check);
#endif

#ifndef BOOST_NO_EXCEPTIONS
        try
        {
#endif

                int size = file_size(argv[1]);
                if (size > 10 * 1000000)
                {
                        std::cerr << "file too big (" << size << "), aborting\n";
                        return 1;
                }
                std::vector<char> buf(size);
                std::ifstream(argv[1], std::ios_base::binary).read(&buf[0], size);
                lazy_entry e;
                int ret = lazy_bdecode(&buf[0], &buf[0] + buf.size(), e);

                if (ret != 0)
                {
                        std::cerr << "invalid bencoding: " << ret << std::endl;
                        return 1;
                }

                std::cout << "\n\n----- raw info -----\n\n";
                std::cout << e << std::endl;

                torrent_info t(e);

                // print info about torrent
                std::cout << "\n\n----- torrent file info -----\n\n";
                std::cout << "nodes:\n";
                typedef std::vector<std::pair<std::string, int> > node_vec;
                node_vec const& nodes = t.nodes();
                for (node_vec::const_iterator i = nodes.begin(), end(nodes.end());
                        i != end; ++i)
                {
                        std::cout << i->first << ":" << i->second << "\n";
                }
                std::cout << "trackers:\n";
                for (std::vector<announce_entry>::const_iterator i = t.trackers().begin();
                        i != t.trackers().end(); ++i)
                {
                        std::cout << i->tier << ": " << i->url << "\n";
                }

                std::cout << "number of pieces: " << t.num_pieces() << "\n";
                std::cout << "piece length: " << t.piece_length() << "\n";
                std::cout << "info hash: " << t.info_hash() << "\n";
                std::cout << "comment: " << t.comment() << "\n";
                std::cout << "created by: " << t.creator() << "\n";
                std::cout << "files:\n";
                int index = 0;
                for (torrent_info::file_iterator i = t.begin_files();
                        i != t.end_files(); ++i, ++index)
                {
                        int first = t.map_file(index, 0, 1).piece;
                        int last = t.map_file(index, i->size - 1, 1).piece;
                        std::cout << "  " << std::setw(11) << i->size
                                << " " << i->path.string() << "[ " << first << ", "
                                << last << " ]\n";
                }

#ifndef BOOST_NO_EXCEPTIONS
        }
        catch (std::exception& e)
        {
                std::cout << e.what() << "\n";
        }
#endif

        return 0;
}

simple client

This is a simple client. It doesn't have much output to keep it simple:

int main(int argc, char* argv[])
{
        using namespace libtorrent;
#if BOOST_VERSION < 103400
        namespace fs = boost::filesystem;
        fs::path::default_name_check(fs::no_check);
#endif

if (argc != 2)
{
        std::cerr << "usage: ./simple_client torrent-file\n"
                "to stop the client, press return.\n";
        return 1;
}

#ifndef BOOST_NO_EXCEPTIONS
        try
#endif
        {
                session s;
                s.listen_on(std::make_pair(6881, 6889));
                add_torrent_params p;
                p.save_path = "./";
                p.ti = new torrent_info(argv[1]);
                s.add_torrent(p);

                // wait for the user to end
                char a;
                std::cin.unsetf(std::ios_base::skipws);
                std::cin >> a;
        }
#ifndef BOOST_NO_EXCEPTIONS
        catch (std::exception& e)
        {
                std::cout << e.what() << "\n";
        }
#endif
        return 0;
}

make_torrent

Shows how to create a torrent from a directory tree:

#include <iostream>
#include <fstream>
#include <iterator>
#include <iomanip>

#include "libtorrent/entry.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/torrent_info.hpp"
#include "libtorrent/file.hpp"
#include "libtorrent/storage.hpp"
#include "libtorrent/hasher.hpp"
#include "libtorrent/create_torrent.hpp"

#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>
#include <boost/filesystem/fstream.hpp>
#include <boost/bind.hpp>

using namespace boost::filesystem;
using namespace libtorrent;

// do not include files and folders whose
// name starts with a .
bool file_filter(boost::filesystem::path const& filename)
{
        if (filename.leaf()[0] == '.') return false;
        std::cerr << filename << std::endl;
        return true;
}

void print_progress(int i, int num)
{
        std::cerr << "\r" << (i+1) << "/" << num;
}

int main(int argc, char* argv[])
{
        using namespace libtorrent;
        using namespace boost::filesystem;

        int piece_size = 256 * 1024;
        char const* creator_str = "libtorrent";

        path::default_name_check(no_check);

        if (argc != 4 && argc != 5)
        {
                std::cerr << "usage: make_torrent <output torrent-file> "
                "<announce url> <file or directory to create torrent from> "
                "[url-seed]\n";
        return 1;
}

#ifndef BOOST_NO_EXCEPTIONS
        try
        {
#endif
                file_storage fs;
                file_pool fp;
                path full_path = complete(path(argv[3]));

                add_files(fs, full_path, file_filter);

                create_torrent t(fs, piece_size);
                t.add_tracker(argv[2]);
                set_piece_hashes(t, full_path.branch_path()
                        , boost::bind(&print_progress, _1, t.num_pieces()));
                std::cerr << std::endl;
                t.set_creator(creator_str);

                if (argc == 5) t.add_url_seed(argv[4]);

                // create the torrent and print it to out
                ofstream out(complete(path(argv[1])), std::ios_base::binary);
                bencode(std::ostream_iterator<char>(out), t.generate());
#ifndef BOOST_NO_EXCEPTIONS
        }
        catch (std::exception& e)
        {
                std::cerr << e.what() << "\n";
        }
#endif

        return 0;
}