diff --git a/pyproject.toml b/pyproject.toml
index b6f6921..20c3176 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,6 +38,7 @@ dev = [
     "ruff>=0.1",
     "mypy>=1.0",
     "types-PyYAML>=6.0",
+    "pandas-stubs>=2.0",
 ]
 
 [project.scripts]
diff --git a/src/py_dvt_ate/instruments/transport/server.py b/src/py_dvt_ate/instruments/transport/server.py
index dc1382c..94ee194 100644
--- a/src/py_dvt_ate/instruments/transport/server.py
+++ b/src/py_dvt_ate/instruments/transport/server.py
@@ -217,10 +217,13 @@ class InstrumentServer:
                 response = instrument.process(command)
 
                 # Send response with newline terminator
+                # Always send a response, even if empty (for acknowledgment)
+                writer.write(f"{response}\n".encode())
+                await writer.drain()
                 if response:
-                    writer.write(f"{response}\n".encode())
-                    await writer.drain()
                     logger.debug("Port %d sent: %s", port, response)
+                else:
+                    logger.debug("Port %d sent: <empty response>", port)
 
         except asyncio.CancelledError:
             logger.debug("Client handler cancelled for port %d", port)