Fix: Prepend simtime to ZMQ write() payload for consistency (Issue #244)

concore.py

@@ -298,6 +298,12 @@ def read(port_identifier, name, initstr_val):
         zmq_p = zmq_ports[port_identifier]
         try:
             message = zmq_p.recv_json_with_retry()
+            # Strip simtime prefix if present (mirroring file-based read behavior)
+            if isinstance(message, list) and len(message) > 0:
+                first_element = message[0]
+                if isinstance(first_element, (int, float)):
+                    simtime = max(simtime, first_element)
+                    return message[1:]
             return message
         except zmq.error.ZMQError as e:
             logging.error(f"ZMQ read error on port {port_identifier} (name: {name}): {e}. Returning default.")
@@ -365,7 +371,7 @@ def read(port_identifier, name, initstr_val):
 def write(port_identifier, name, val, delta=0):
     """
     Write data either to ZMQ port or file.
-    `val` must be list (with simtime prefix) or string.
+    `val` is the data payload (list or string); write() prepends [simtime + delta] internally.
     """
     global simtime
 
@@ -375,7 +381,13 @@ def write(port_identifier, name, val, delta=0):
         try:
             # Keep ZMQ payloads JSON-serializable by normalizing numpy types.
             zmq_val = convert_numpy_to_python(val)
-            zmq_p.send_json_with_retry(zmq_val)
+            if isinstance(zmq_val, list):
+                # Prepend simtime to match file-based write behavior
+                payload = [simtime + delta] + zmq_val
+                zmq_p.send_json_with_retry(payload)
+                simtime += delta
+            else:
+                zmq_p.send_json_with_retry(zmq_val)
         except zmq.error.ZMQError as e:
             logging.error(f"ZMQ write error on port {port_identifier} (name: {name}): {e}")
         except Exception as e:

tests/test_concore.py

@@ -236,11 +236,43 @@ def send_json_with_retry(self, message):
         dummy = DummyPort()
         concore.zmq_ports["test_zmq"] = dummy
 
+        # Reset simtime for predictable test behavior
+        concore.simtime = 0
+
         payload = [np.int64(7), np.float64(3.5), {"x": np.float32(1.25)}]
         concore.write("test_zmq", "data", payload)
 
         assert dummy.sent is not None
-        assert dummy.sent == [7, 3.5, {"x": 1.25}]
-        assert not isinstance(dummy.sent[0], np.generic)
+        # ZMQ write now prepends simtime (0 in this case) to match file-based write behavior
+        assert dummy.sent == [0, 7, 3.5, {"x": 1.25}]
+        # Data values (after simtime) should be converted from numpy types
         assert not isinstance(dummy.sent[1], np.generic)
-        assert not isinstance(dummy.sent[2]["x"], np.generic)
+        assert not isinstance(dummy.sent[2], np.generic)
+        assert not isinstance(dummy.sent[3]["x"], np.generic)
+
+    def test_zmq_write_read_roundtrip(self):
+        """Test that ZMQ write+read returns original data without simtime prefix."""
+        import concore
+
+        class DummyZMQPort:
+            def __init__(self):
+                self.buffer = None
+
+            def send_json_with_retry(self, message):
+                self.buffer = message
+
+            def recv_json_with_retry(self):
+                return self.buffer
+
+        dummy = DummyZMQPort()
+        concore.zmq_ports["roundtrip_test"] = dummy
+
+        # Reset simtime for predictable test behavior
+        concore.simtime = 0
+
+        original_data = [1.5, 2.5, 3.5]
+        concore.write("roundtrip_test", "data", original_data)
+
+        # Read should return original data (simtime stripped)
+        result = concore.read("roundtrip_test", "data", "[]")
+        assert result == original_data