// Announce announces using UDP format
func (u UDPTracker) Announce(query url.Values, file data.FileRecord) []byte {
// Create UDP announce response
announce := udp.AnnounceResponse{
Action: 1,
TransID: u.TransID,
Interval: uint32(common.Static.Config.Interval),
Leechers: uint32(file.Leechers()),
Seeders: uint32(file.Seeders()),
}
// Convert to UDP byte buffer
announceBuf, err := announce.MarshalBinary()
if err != nil {
log.Println(err.Error())
return u.Error("Could not create UDP announce response")
}
// Numwant
numwant, err := strconv.Atoi(query.Get("numwant"))
if err != nil {
numwant = 50
}
// Add compact peer list
res := bytes.NewBuffer(announceBuf)
err = binary.Write(res, binary.BigEndian, file.PeerList(query.Get("ip"), numwant))
if err != nil {
log.Println(err.Error())
return u.Error("Could not create UDP announce response")
}
return res.Bytes()
}
// Announce announces using HTTP format
func (h HTTPTracker) Announce(query url.Values, file data.FileRecord) []byte {
// Generate response struct
announce := AnnounceResponse{
Complete: file.Seeders(),
Incomplete: file.Leechers(),
Interval: common.Static.Config.Interval,
MinInterval: common.Static.Config.Interval / 2,
}
// Check for numwant parameter, return up to that number of peers
// Default is 50 per protocol
numwant := 50
if query.Get("numwant") != "" {
// Verify numwant is an integer
num, err := strconv.Atoi(query.Get("numwant"))
if err == nil {
numwant = num
}
}
// Marshal struct into bencode
buf := bytes.NewBuffer(make([]byte, 0))
if err := bencode.Marshal(buf, announce); err != nil {
log.Println(err.Error())
return h.Error("Tracker error: failed to create announce response")
}
// Generate compact peer list of length numwant, exclude this user
peers := file.PeerList(query.Get("ip"), numwant)
// Because the bencode marshaler does not handle compact, binary peer list conversion,
// we handle it manually here.
// Get initial buffer, chop off 3 bytes: "0:e", append the actual list length with new colon
out := buf.Bytes()
out = append(out[0:len(out)-3], []byte(strconv.Itoa(len(peers))+":")...)
// Append peers list, terminate with an "e"
out = append(append(out, peers...), byte('e'))
// Return final announce message
return out
}