diff --git a/app/internal/socks5/server.go b/app/internal/socks5/server.go
index 5fefb45..e451637 100644
--- a/app/internal/socks5/server.go
+++ b/app/internal/socks5/server.go
@@ -254,6 +254,7 @@ func (s *Server) udpServer(udpConn *net.UDPConn, hyUDP client.HyUDPConn) error {
 					if err != nil {
 						continue
 					}
+					addr = addr[1:] // Remove the leading length byte
 					d := socks5.NewDatagram(atyp, addr, port, bs)
 					_, _ = udpConn.WriteToUDP(d.Bytes(), clientAddr)
 				}
diff --git a/app/internal/socks5/server_test.go b/app/internal/socks5/server_test.go
new file mode 100644
index 0000000..5fcb103
--- /dev/null
+++ b/app/internal/socks5/server_test.go
@@ -0,0 +1,128 @@
+package socks5
+
+import (
+	"io"
+	"net"
+	"os/exec"
+	"testing"
+	"time"
+
+	"github.com/apernet/hysteria/core/client"
+)
+
+type mockEchoHyClient struct{}
+
+func (c *mockEchoHyClient) DialTCP(addr string) (net.Conn, error) {
+	return &mockEchoTCPConn{
+		BufChan: make(chan []byte, 10),
+	}, nil
+}
+
+func (c *mockEchoHyClient) ListenUDP() (client.HyUDPConn, error) {
+	return &mockEchoUDPConn{
+		BufChan: make(chan mockEchoUDPPacket, 10),
+	}, nil
+}
+
+func (c *mockEchoHyClient) Close() error {
+	return nil
+}
+
+type mockEchoTCPConn struct {
+	BufChan chan []byte
+}
+
+func (c *mockEchoTCPConn) Read(b []byte) (n int, err error) {
+	buf := <-c.BufChan
+	if buf == nil {
+		// EOF
+		return 0, io.EOF
+	}
+	return copy(b, buf), nil
+}
+
+func (c *mockEchoTCPConn) Write(b []byte) (n int, err error) {
+	c.BufChan <- b
+	return len(b), nil
+}
+
+func (c *mockEchoTCPConn) Close() error {
+	close(c.BufChan)
+	return nil
+}
+
+func (c *mockEchoTCPConn) LocalAddr() net.Addr {
+	// Not implemented
+	return nil
+}
+
+func (c *mockEchoTCPConn) RemoteAddr() net.Addr {
+	// Not implemented
+	return nil
+}
+
+func (c *mockEchoTCPConn) SetDeadline(t time.Time) error {
+	// Not implemented
+	return nil
+}
+
+func (c *mockEchoTCPConn) SetReadDeadline(t time.Time) error {
+	// Not implemented
+	return nil
+}
+
+func (c *mockEchoTCPConn) SetWriteDeadline(t time.Time) error {
+	// Not implemented
+	return nil
+}
+
+type mockEchoUDPPacket struct {
+	Data []byte
+	Addr string
+}
+
+type mockEchoUDPConn struct {
+	BufChan chan mockEchoUDPPacket
+}
+
+func (c *mockEchoUDPConn) Receive() ([]byte, string, error) {
+	p := <-c.BufChan
+	if p.Data == nil {
+		// EOF
+		return nil, "", io.EOF
+	}
+	return p.Data, p.Addr, nil
+}
+
+func (c *mockEchoUDPConn) Send(bytes []byte, s string) error {
+	c.BufChan <- mockEchoUDPPacket{
+		Data: bytes,
+		Addr: s,
+	}
+	return nil
+}
+
+func (c *mockEchoUDPConn) Close() error {
+	close(c.BufChan)
+	return nil
+}
+
+func TestServer(t *testing.T) {
+	// Start the server
+	s := &Server{
+		HyClient: &mockEchoHyClient{},
+	}
+	l, err := net.Listen("tcp", "127.0.0.1:11080")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer l.Close()
+	go s.Serve(l)
+
+	// Run the Python test script
+	cmd := exec.Command("python", "server_test.py")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("Failed to run test script: %v\n%s", err, out)
+	}
+}
diff --git a/app/internal/socks5/server_test.py b/app/internal/socks5/server_test.py
new file mode 100644
index 0000000..4515561
--- /dev/null
+++ b/app/internal/socks5/server_test.py
@@ -0,0 +1,38 @@
+import socket
+import socks
+import os
+
+ADDR = "127.0.0.1"
+PORT = 11080
+
+
+def test_tcp(size, count, it):
+    for i in range(it):
+        s = socks.socksocket(socket.AF_INET, socket.SOCK_STREAM)
+        s.set_proxy(socks.SOCKS5, ADDR, PORT)
+
+        s.connect(("test_tcp", 12345))
+        for j in range(count):
+            payload = os.urandom(size)
+            s.send(payload)
+            rsp = s.recv(size)
+            assert rsp == payload
+        s.close()
+
+
+def test_udp(size, count, it):
+    for i in range(it):
+        s = socks.socksocket(socket.AF_INET, socket.SOCK_DGRAM)
+        s.set_proxy(socks.SOCKS5, ADDR, PORT)
+
+        for j in range(count):
+            payload = os.urandom(size)
+            s.sendto(payload, ("test_udp", 12345))
+            rsp, addr = s.recvfrom(size)
+            assert rsp == payload and addr == (b"test_udp", 12345)
+        s.close()
+
+
+if __name__ == "__main__":
+    test_tcp(1024, 1024, 10)
+    test_udp(1024, 1024, 10)