66 lines
1.3 KiB
Go
66 lines
1.3 KiB
Go
package multicast
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import (
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"net"
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"sync"
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)
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type PacketHandler func(net.Addr, []byte) error
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type AddrResolver struct {
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Addr string
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mu sync.RWMutex
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udp *net.UDPAddr
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err error
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}
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func (r *AddrResolver) setAddress(addr string) {
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r.mu.Lock()
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r.Addr = addr
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r.udp = nil
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r.err = nil
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r.mu.Unlock()
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}
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func (r *AddrResolver) resolve() (*net.UDPAddr, error) {
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r.mu.RLock()
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if err := r.err; err != nil {
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r.mu.RUnlock()
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return nil, err
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}
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if udp := r.udp; udp != nil {
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r.mu.RUnlock()
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return udp, nil
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}
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r.mu.RUnlock()
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r.mu.Lock()
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defer r.mu.Unlock()
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r.udp, r.err = net.ResolveUDPAddr("udp4", r.Addr)
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return r.udp, r.err
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}
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var RecvAddrResolver = &AddrResolver{Addr: "224.0.0.1:1900"}
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// SetRecvAddrIPv4 updates multicast address where to receive packets.
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// This never fail now.
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func SetRecvAddrIPv4(addr string) error {
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RecvAddrResolver.setAddress(addr)
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return nil
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}
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var sendAddrResolver = &AddrResolver{Addr: "239.255.255.250:1900"}
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// SendAddr returns an address to send multicast UDP package.
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func SendAddr() (*net.UDPAddr, error) {
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return sendAddrResolver.resolve()
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}
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// SetSendAddrIPv4 updates a UDP address to send multicast packets.
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// This never fail now.
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func SetSendAddrIPv4(addr string) error {
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sendAddrResolver.setAddress(addr)
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return nil
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}
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