// 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),
}
// Calculate file seeders and leechers
seeders, err := file.Seeders()
if err != nil {
log.Println(err.Error())
}
announce.Seeders = uint32(seeders)
leechers, err := file.Leechers()
if err != nil {
log.Println(err.Error())
}
announce.Leechers = uint32(leechers)
// Convert to UDP byte buffer
announceBuf, err := announce.MarshalBinary()
if err != nil {
log.Println(err.Error())
return u.Error(ErrAnnounceFailure.Error())
}
// Numwant
numwant, err := strconv.Atoi(query.Get("numwant"))
if err != nil {
numwant = 50
}
// Retrieve compact peer list
// Note: because we are UDP, we send the second parameter 'false' to get
// a "best guess" peer list, due to anonymous announces
peers, err := file.CompactPeerList(numwant, false)
if err != nil {
log.Println(err.Error())
return u.Error(ErrPeerListFailure.Error())
}
// Add compact peer list
res := bytes.NewBuffer(announceBuf)
err = binary.Write(res, binary.BigEndian, peers)
if err != nil {
log.Println(err.Error())
return u.Error(ErrPeerListFailure.Error())
}
return res.Bytes()
}
