basic wake-on-lan actuator

2 files changed, 85 insertions, 0 deletions

diff --git a/wakeonlan/wakeonlan.go b/wakeonlan/wakeonlan.go
new file mode 100644
index 0000000..803d27f
--- /dev/null
+++ b/wakeonlan/wakeonlan.go
@@ -0,0 +1,43 @@
+// Package wakeonlan implements Wake-On-Lan.
+package wakeonlan
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"net"
+)
+
+var (
+	header = []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}
+
+	broadcastAddr = &net.UDPAddr{
+		IP:   net.IPv4bcast,
+		Port: 9,
+	}
+)
+
+// Wake sends the Magic Packet to wake the computer with the given MAC address.
+func Wake(mac net.HardwareAddr) error {
+	conn, err := net.DialUDP("udp", nil, broadcastAddr)
+	if err != nil {
+		return fmt.Errorf("could not create UDP broadcast: %w", err)
+	}
+	defer conn.Close()
+
+	payload := packet(mac)
+
+	if _, err := conn.Write(payload); err != nil {
+		return fmt.Errorf("could not send Magic Packet: %w", err)
+	}
+	return nil
+}
+
+func packet(mac net.HardwareAddr) []byte {
+	var buf bytes.Buffer
+	binary.Write(&buf, binary.BigEndian, header)
+	for i := 0; i < 16; i++ {
+		binary.Write(&buf, binary.BigEndian, mac)
+	}
+	return buf.Bytes()
+}
diff --git a/wakeonlan/wakeonlan_test.go b/wakeonlan/wakeonlan_test.go
new file mode 100644
index 0000000..245d580
--- /dev/null
+++ b/wakeonlan/wakeonlan_test.go
@@ -0,0 +1,42 @@
+package wakeonlan
+
+import (
+	"encoding/hex"
+	"net"
+	"reflect"
+	"testing"
+)
+
+func TestPacket(t *testing.T) {
+	tests := []struct {
+		mac    string
+		packet string
+	}{
+		{
+			"a8:23:22:ad:be:c7",
+			"ffffffffffffa82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7a82322adbec7",
+		},
+	}
+
+	for i, test := range tests {
+		mac, err := net.ParseMAC(test.mac)
+		if err != nil {
+			t.Fatalf("invalid MAC address %q: %v", test.mac, err)
+		}
+
+		if len(test.packet) != 102 {
+			if err != nil {
+				t.Fatalf("invalid packet length address: found %v, want 102", len(test.packet))
+			}
+		}
+		want, err := hex.DecodeString(test.packet)
+		if err != nil {
+			t.Fatalf("invalid hex string: %v", err)
+		}
+
+		got := packet(mac)
+		if !reflect.DeepEqual(want, got) {
+			t.Errorf("[test %d]\nwanted %v\nlen %d\ngot %v\nlen %d", i, want, len(want), got, len(got))
+		}
+	}
+}