Ack and keep alive to not time out

packet/packet.go

@@ -1,5 +1,7 @@
 package packet
 
+import "slices"
+
 const (
 	packetFlagControl     = 1
 	packetFlagResend      = 2
@@ -19,6 +21,43 @@ type PacketHeader struct {
 	Ack       int
 	NumChunks int
 	Token     [4]byte
+
+	// connless
+	ResponseToken [4]byte
+}
+
+func (header *PacketHeader) Pack() []byte {
+	flags := 0
+	if header.Flags.Control {
+		flags |= packetFlagControl
+	}
+	if header.Flags.Resend {
+		flags |= packetFlagResend
+	}
+	if header.Flags.Compression {
+		flags |= packetFlagCompression
+	}
+	if header.Flags.Connless {
+		flags |= packetFlagConnless
+	}
+
+	if header.Flags.Connless {
+		version := 1
+		return slices.Concat(
+			[]byte{byte(((packetFlagConnless << 2) & 0x0fc) | (version & 0x03))},
+			header.Token[:],
+			header.ResponseToken[:],
+		)
+	}
+
+	return slices.Concat(
+		[]byte{
+			byte(((flags << 2) & 0xfc) | ((header.Ack >> 8) & 0x03)),
+			byte(header.Ack & 0x0ff),
+			byte(header.NumChunks),
+		},
+		header.Token[:],
+	)
 }
 
 func (header *PacketHeader) Unpack(packet []byte) {

packet/packet_test.go

@@ -6,7 +6,29 @@ import (
 	"testing"
 )
 
-// pack
+// pack header
+
+func TestPackHeader(t *testing.T) {
+	header := PacketHeader{
+		Flags: PacketFlags{
+			Connless:    false,
+			Compression: false,
+			Resend:      false,
+			Control:     true,
+		},
+		Ack:       10,
+		NumChunks: 0,
+		Token:     [4]byte{0xcf, 0x2e, 0xde, 0x1d},
+	}
+	got := header.Pack()
+	want := []byte{0x04, 0x0a, 0x00, 0xcf, 0x2e, 0xde, 0x1d}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %v, wanted %v", got, want)
+	}
+}
+
+// pack flags
 
 func TestPackFlagsUnset(t *testing.T) {
 	flags := PacketFlags{

teeworlds.go

@@ -18,6 +18,7 @@ import (
 const (
 	maxPacksize = 1400
 
+	msgCtrlKeepAlive = 0x00
 	msgCtrlConnect   = 0x01
 	msgCtrlAccept    = 0x02
 	msgCtrlToken     = 0x05
@@ -25,6 +26,7 @@ const (
 
 	msgSysMapChange  = 2
 	msgSysConReady   = 5
+	msgSysSnapSingle = 8
 
 	msgGameReadyToEnter = 8
 	msgGameMotd         = 1
@@ -68,12 +70,24 @@ type TeeworldsClient struct {
 	clientToken [4]byte
 	serverToken [4]byte
 	conn        net.Conn
+
+	Ack int
 }
 
 func (client TeeworldsClient) sendCtrlMsg(data []byte) {
-	flags := []byte{0x04, 0x00, 0x00}
-	packet := slices.Concat(flags, client.serverToken[:], data)
+	header := packet.PacketHeader{
+		Flags: packet.PacketFlags{
+			Connless:    false,
+			Compression: false,
+			Resend:      false,
+			Control:     true,
+		},
+		Ack:       client.Ack,
+		NumChunks: 0,
+		Token:     client.serverToken,
+	}
 
+	packet := slices.Concat(header.Pack(), data)
 	client.conn.Write(packet)
 }
 
@@ -86,6 +100,10 @@ func (client TeeworldsClient) sendReady() {
 	client.conn.Write(packet)
 }
 
+func (client TeeworldsClient) sendKeepAlive() {
+	client.sendCtrlMsg([]byte{msgCtrlKeepAlive})
+}
+
 func (client TeeworldsClient) sendInfo() {
 	info := []byte{0x40, 0x28, 0x01, 0x03, 0x30, 0x2E, 0x37, 0x20, 0x38, 0x30, 0x32, 0x66,
 		0x31, 0x62, 0x65, 0x36, 0x30, 0x61, 0x30, 0x35, 0x36, 0x36, 0x35, 0x66,
@@ -176,6 +194,10 @@ func (client *TeeworldsClient) onSystemMsg(msg int, chunk chunk.Chunk, u *packer
 	} else if msg == msgSysConReady {
 		fmt.Println("got ready")
 		client.sendStartInfo()
+	} else if msg == msgSysSnapSingle {
+		tick := u.GetInt()
+		fmt.Printf("got snap single tick=%d\n", tick)
+		client.sendKeepAlive()
 	} else {
 		fmt.Printf("unknown system message id=%d data=%x\n", msg, chunk.Data)
 	}
@@ -193,6 +215,10 @@ func (client *TeeworldsClient) onGameMsg(msg int, chunk chunk.Chunk, u *packer.U
 func (client *TeeworldsClient) onMessage(chunk chunk.Chunk) {
 	fmt.Printf("got chunk size=%d data=%v\n", chunk.Header.Size, chunk.Data)
 
+	if chunk.Header.Flags.Vital {
+		client.Ack++
+	}
+
 	u := packer.Unpacker{}
 	u.Reset(chunk.Data)