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package soundbox
import (
"context"
"fmt"
"net"
"time"
)
// streamingPort is the default network port a soundbox is listening to for
// incoming audio stream data.
const streamingPort = 5316
const dialTimeoutSeconds = 3
// toLinkLocal converts a MAC address to the corresponding IPv6 link-local
// address.
func toLinkLocal(ha net.HardwareAddr) (net.IP, error) {
switch len(ha) {
case 6:
ip := net.IP{0xfe, 0x80, 0, 0, 0, 0, 0, 0,
ha[0] ^ 0b10, ha[1], ha[2], 0xff, 0xfe, ha[3], ha[4], ha[5]}
return ip, nil
default:
return nil, fmt.Errorf("Only IEEE 802 MAC-48 addresses supported")
}
}
func dialContext(ctx context.Context, ha net.HardwareAddr) (net.Conn, error) {
ip, err := toLinkLocal(ha)
if err != nil {
return nil, err
}
ifaces, err := net.Interfaces()
if err != nil {
return nil, err
}
c := make(chan net.Conn)
dialContext, cancel := context.WithTimeout(ctx, dialTimeoutSeconds*time.Second)
defer cancel()
for _, iface := range ifaces {
go func() {
var d net.Dialer
conn, err := d.DialContext(
ctx,
"tcp6",
fmt.Sprintf("[%s%%%s]:%d", ip, iface.Name, streamingPort),
)
if err == nil {
c <- conn
}
}()
}
select {
case conn := <-c:
return conn, nil
case <-dialContext.Done():
return nil, fmt.Errorf("Could not dial TCP connection to %v on port %d on any interface.", ha, streamingPort)
}
}
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