# libtorrent Examples

Author: | Arvid Norberg, arvid@rasterbar.com

Table of contents

- examples
  - dump_torrent
  - simple client
  - make_torrent

# 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;
    }