diff --git a/xmpp_agent_core.py b/xmpp_agent_core.py
index b726267..909d07d 100644
--- a/xmpp_agent_core.py
+++ b/xmpp_agent_core.py
@@ -246,8 +246,9 @@ def _rdp_health_check():
     import socket as _sk
     try:
         _s = _sk.create_connection(('127.0.0.1', 3389), timeout=5)
-        # X.224 Connection Request + RDP Negotiation Request (HYBRID)
-        _s.sendall(bytes.fromhex('0300001b13e0000000000001000800020000000000000000000000000'))
+        # X.224 Connection Request + RDP Negotiation Request (SSL|HYBRID|RDSTLS)
+        # TPKT len=0x13(19) 必须等于实际包长，否则服务器正确 RST（2026-07-22 误诊教训）
+        _s.sendall(bytes.fromhex('030000130ee00000000000010008000b000000'))
         _s.settimeout(5)
         _resp = _s.recv(1024)
         _s.close()