Update simple.py

**Summary of Changes**
1. Explicit UTF-8 Encoding:

- Both the topic and msg are now explicitly encoded using UTF-8 (topic.encode('utf-8') and msg.encode('utf-8')).
- This ensures that multi-byte characters are correctly represented.


2. Accurate Size Calculation:

- The size of the message (sz) is calculated based on the byte length of the encoded topic and message

Signed-off-by: FallenPhoenix8 <[email protected]>

Author: FallenPhoenix8

micropython/umqtt.simple/umqtt/simple.py

@@ -115,39 +115,49 @@ def ping(self):
         self.sock.write(b"\xc0\0")
 
     def publish(self, topic, msg, retain=False, qos=0):
-        pkt = bytearray(b"\x30\0\0\0")
-        pkt[0] |= qos << 1 | retain
-        sz = 2 + len(topic) + len(msg)
-        if qos > 0:
-            sz += 2
-        assert sz < 2097152
-        i = 1
-        while sz > 0x7F:
-            pkt[i] = (sz & 0x7F) | 0x80
-            sz >>= 7
-            i += 1
-        pkt[i] = sz
-        # print(hex(len(pkt)), hexlify(pkt, ":"))
-        self.sock.write(pkt, i + 1)
-        self._send_str(topic)
-        if qos > 0:
-            self.pid += 1
-            pid = self.pid
-            struct.pack_into("!H", pkt, 0, pid)
-            self.sock.write(pkt, 2)
-        self.sock.write(msg)
-        if qos == 1:
-            while 1:
-                op = self.wait_msg()
-                if op == 0x40:
-                    sz = self.sock.read(1)
-                    assert sz == b"\x02"
-                    rcv_pid = self.sock.read(2)
-                    rcv_pid = rcv_pid[0] << 8 | rcv_pid[1]
-                    if pid == rcv_pid:
-                        return
-        elif qos == 2:
-            assert 0
+    print(f"Preparing to publish: topic={topic}, msg={msg}, retain={retain}, qos={qos}")
+
+    # Encode the topic and message in UTF-8
+    topic = topic.encode('utf-8')
+    msg = msg.encode('utf-8')
+
+    # Calculate the size of the message
+    sz = 2 + len(topic) + len(msg)
+    if qos > 0:
+        sz += 2
+
+    assert sz < 2097152  # MQTT supports a maximum of 2MB messages
+    print(f"Calculated message size: {sz}")
+
+    # Create the packet header
+    pkt = bytearray(5)  # Header can be up to 5 bytes
+    pkt[0] = 0x30 | (qos << 1) | retain  # Message type (PUBLISH)
+    i = 1
+    while sz > 0x7F:  # Multi-byte length encoding
+        pkt[i] = (sz & 0x7F) | 0x80
+        sz >>= 7
+        i += 1
+    pkt[i] = sz
+
+    # Send the header and data
+    self.sock.write(pkt[:i + 1])  # Header
+    self._send_str(topic)  # Topic
+    self.sock.write(msg)  # Message
+    print(f"Message sent: {msg.decode('utf-8')}")
+
+    # QoS handling
+    if qos == 1:
+        while True:
+            op = self.wait_msg()
+            if op == 0x40:
+                sz = self.sock.read(1)
+                assert sz == b'\x02'
+                rcv_pid = self.sock.read(2)
+                rcv_pid = rcv_pid[0] << 8 | rcv_pid[1]
+                if self.pid == rcv_pid:
+                    return
+    elif qos == 2:
+        raise NotImplementedError("QoS level 2 not implemented")
 
     def subscribe(self, topic, qos=0):
         assert self.cb is not None, "Subscribe callback is not set"