diff --git a/README.en.md b/README.en.md
index fc6fa03..f665b81 100644
--- a/README.en.md
+++ b/README.en.md
@@ -86,6 +86,7 @@ Additional flags:
 - `-turn <ip>`: override TURN server address.
 - `-port <port>`: override TURN server port.
 - `-no-dtls`: without DTLS obfuscation (may result in a ban).
+- `-v1`: use v1 protocol (no session_id and stream_id sent). For legacy servers.
 
 #### Linux
 
diff --git a/README.md b/README.md
index f1aeca5..54155fd 100644
--- a/README.md
+++ b/README.md
@@ -87,6 +87,7 @@ chmod 777 ./client-android
 - `-turn <ip>`: переопределить адрес TURN сервера.
 - `-port <port>`: переопределить порт TURN сервера.
 - `-no-dtls`: без DTLS-обфускации (может привести к бану).
+- `-v1`: использовать протокол v1 (без отправки session_id и stream_id). Для серверов старой версии.
 
 #### Linux
 
diff --git a/client/main.go b/client/main.go
index 3e19922..001e127 100644
--- a/client/main.go
+++ b/client/main.go
@@ -52,7 +52,7 @@ func dtlsFunc(ctx context.Context, conn net.PacketConn, peer *net.UDPAddr) (net.
 	return dtlsConn, nil
 }
 
-func oneDtlsConnection(ctx context.Context, peer *net.UDPAddr, listenConn net.PacketConn, connchan chan<- net.PacketConn, okchan chan<- struct{}, c chan<- error, sessionID []byte, streamID byte) {
+func oneDtlsConnection(ctx context.Context, peer *net.UDPAddr, listenConn net.PacketConn, connchan chan<- net.PacketConn, okchan chan<- struct{}, c chan<- error, sessionID []byte, streamID byte, v1 bool) {
 	var err error = nil
 	defer func() { c <- err }()
 	dtlsctx, dtlscancel := context.WithCancel(ctx)
@@ -81,17 +81,20 @@ func oneDtlsConnection(ctx context.Context, peer *net.UDPAddr, listenConn net.Pa
 		log.Printf("Closed DTLS connection\n")
 	}()
 
-	// Phase 1: Send Session ID + Stream ID (17 bytes)
-	dtlsConn.SetWriteDeadline(time.Now().Add(time.Second * 5))
-	idBuf := make([]byte, 17)
-	copy(idBuf[:16], sessionID)
-	idBuf[16] = streamID
-	if _, err1 = dtlsConn.Write(idBuf); err1 != nil {
-		err = fmt.Errorf("failed to send session ID: %s", err1)
-		return
+	// Phase 1: Send Session ID + Stream ID (17 bytes) - only for v2 protocol
+	if !v1 {
+		dtlsConn.SetWriteDeadline(time.Now().Add(time.Second * 5))
+		idBuf := make([]byte, 17)
+		copy(idBuf[:16], sessionID)
+		idBuf[16] = streamID
+		if _, err1 = dtlsConn.Write(idBuf); err1 != nil {
+			err = fmt.Errorf("failed to send session ID: %s", err1)
+			return
+		}
+		log.Printf("Established DTLS connection and sent session ID with stream %d!\n", streamID)
+	} else {
+		log.Printf("Established DTLS connection (v1 protocol, no session ID)!\n")
 	}
-
-	log.Printf("Established DTLS connection and sent session ID with stream %d!\n", streamID)
 	go func() {
 		for {
 			select {
@@ -369,14 +372,14 @@ func oneTurnConnection(ctx context.Context, turnParams *turnParams, peer *net.UD
 	conn2.SetDeadline(time.Time{})
 }
 
-func oneDtlsConnectionLoop(ctx context.Context, peer *net.UDPAddr, listenConnChan <-chan net.PacketConn, connchan chan<- net.PacketConn, okchan chan<- struct{}, sessionID []byte, streamID byte) {
+func oneDtlsConnectionLoop(ctx context.Context, peer *net.UDPAddr, listenConnChan <-chan net.PacketConn, connchan chan<- net.PacketConn, okchan chan<- struct{}, sessionID []byte, streamID byte, v1 bool) {
 	for {
 		select {
 		case <-ctx.Done():
 			return
 		case listenConn := <-listenConnChan:
 			c := make(chan error)
-			go oneDtlsConnection(ctx, peer, listenConn, connchan, okchan, c, sessionID, streamID)
+			go oneDtlsConnection(ctx, peer, listenConn, connchan, okchan, c, sessionID, streamID, v1)
 			if err := <-c; err != nil {
 				log.Printf("%s", err)
 			}
@@ -432,6 +435,7 @@ func main() { //nolint:cyclop
 	n := flag.Int("n", 0, "connections to TURN (default 4)")
 	udp := flag.Bool("udp", false, "connect to TURN with UDP")
 	direct := flag.Bool("no-dtls", false, "connect without obfuscation. DO NOT USE")
+	v1 := flag.Bool("v1", false, "use v1 server protocol (no session_id and stream_id)")
 	sessionIDFlag := flag.String("session-id", "", "override session ID (hex, 32 chars)")
 	flag.Parse()
 	if *peerAddr == "" {
@@ -525,7 +529,7 @@ func main() { //nolint:cyclop
 		wg1.Add(1)
 		go func() {
 			defer wg1.Done()
-			oneDtlsConnectionLoop(ctx, peer, listenConnChan, connchan, okchan, sessionID, 0)
+			oneDtlsConnectionLoop(ctx, peer, listenConnChan, connchan, okchan, sessionID, 0, *v1)
 		}()
 
 		wg1.Add(1)
@@ -544,7 +548,7 @@ func main() { //nolint:cyclop
 			wg1.Add(1)
 			go func(sID byte) {
 				defer wg1.Done()
-				oneDtlsConnectionLoop(ctx, peer, listenConnChan, connchan, nil, sessionID, sID)
+				oneDtlsConnectionLoop(ctx, peer, listenConnChan, connchan, nil, sessionID, sID, *v1)
 			}(byte(streamID))
 			wg1.Add(1)
 			go func() {