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"


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

        if (argc != 2)
        {
                std::cerr << "usage: dump_torrent torrent-file\n";
                return 1;
        }

        try
        {
                std::ifstream in(argv[1], std::ios_base::binary);
                in.unsetf(std::ios_base::skipws);
                entry e = bdecode(std::istream_iterator<char>(in)
                        , std::istream_iterator<char>());

                std::cout << "\n\n----- raw info -----\n\n";
                e.print(std::cout);

                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";
                for (torrent_info::file_iterator i = t.begin_files();
                        i != t.end_files(); ++i)
                {
                        std::cout << "  " << std::setw(11) << i->size
                                << " " << i->path.string() << "\n";
                }
                
        }
        catch (std::exception& e)
        {
                std::cout << e.what() << "\n";
        }

        return 0;
}

simple client

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

#include <iostream>
#include <fstream>
#include <iterator>
#include <exception>

#include <boost/format.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

#include "libtorrent/entry.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/session.hpp"

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

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

        try
        {
                session s;
                s.listen_on(std::make_pair(6881, 6889));

                std::ifstream in(argv[1], std::ios_base::binary);
                in.unsetf(std::ios_base::skipws);
                entry e = bdecode(std::istream_iterator<char>(in)
                        , std::istream_iterator<char>());
                s.add_torrent(torrent_info(e), "");
                        
                // wait for the user to end
                char a;
                std::cin.unsetf(std::ios_base::skipws);
                std::cin >> a;
        }
        catch (std::exception& e)
        {
                std::cout << e.what() << "\n";
        }
        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/file_pool.hpp"

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

using namespace boost::filesystem;
using namespace libtorrent;

void add_files(
        torrent_info& t
        , path const& p
        , path const& l)
{
        path f(p / l);
        if (is_directory(f))
        {
                for (directory_iterator i(f), end; i != end; ++i)
                        add_files(t, p, l / i->leaf());
        }
        else
        {
                std::cerr << "adding \"" << l.string() << "\"\n";
                t.add_file(l, file_size(f));
        }
}

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

        path::default_name_check(no_check);

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

        try
        {
                torrent_info t;
                path full_path = complete(path(argv[3]));
                ofstream out(complete(path(argv[1])), std::ios_base::binary);

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

                add_files(t, full_path.branch_path(), full_path.leaf());
                t.set_piece_size(piece_size);

                file_pool fp;
                storage st(t, full_path.branch_path(), fp);
                t.add_tracker(argv[2]);

                // calculate the hash for all pieces
                int num = t.num_pieces();
                std::vector<char> buf(piece_size);
                for (int i = 0; i < num; ++i)
                {
                        st.read(&buf[0], i, 0, t.piece_size(i));
                        hasher h(&buf[0], t.piece_size(i));
                        t.set_hash(i, h.final());
                        std::cerr << (i+1) << "/" << num << "\r";
                }

                t.set_creator(creator_str);

                // create the torrent and print it to out
                entry e = t.create_torrent();
                libtorrent::bencode(std::ostream_iterator<char>(out), e);
                }
                catch (std::exception& e)
        {
                std::cerr << e.what() << "\n";
        }

        return 0;
}