func NewSender(mcastAddress string) (*Sender, error) {
var err error
sender := new(Sender)
// One connection is used both to send multicasts and to receive command packets.
// We create the connection by setting up listening for commands packets,
// but can also use the connection to send multicasts.
sender.conn, err = utils.ListenUDP4()
if err != nil {
return nil, err
}
sender.mcast, err = net.ResolveUDPAddr("udp4", mcastAddress)
if err != nil {
return nil, err
}
minAgeSeconds := int32(10)
maxAgeSeconds := int32(20)
maxPayloadMB := uint32(50)
sender.history = history.NewHistory(minAgeSeconds, maxAgeSeconds, maxPayloadMB)
commands := make(chan packet.Packet, 10)
go packet.Listen(sender.conn, commands)
go sender.serveCommand(commands)
return sender, nil
}
func NewReceiver(mcastAddress string) (*Receiver, error) {
receiver := new(Receiver)
addr, err := net.ResolveUDPAddr("udp4", mcastAddress)
if err != nil {
return nil, err
}
receiver.messageConn, err = net.ListenMulticastUDP("udp4", nil, addr)
if err != nil {
return nil, err
}
receiver.controlConn, err = utils.ListenUDP4()
if err != nil {
receiver.messageConn.Close()
return nil, err
}
// Currently there is just one channel that delivers all messages as they are received.
// TODO:
// 1. Track unique senders
// 2. Track sequence numbers of packets from each sender
// 3. Detect dropped packets and send request for packet resend to correct sender.
// 4. Detect duplicate packets and drop them.
// 5. Optionally hold future packets for delivery in correct sequence.
receiver.senders = sendersmap.New()
receiver.incoming = make(chan packet.Packet, 10)
receiver.sequenced = make(chan packet.Packet, 10)
go receiver.AnalyzeAndSequence()
go packet.Listen(receiver.messageConn, receiver.incoming)
return receiver, nil
}