umqtt.simple: Initial implementation of a simple MQTT client.

Author: Paul Sokolovsky

umqtt.simple/umqtt/simple.py

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+import usocket as socket
+import ustruct as struct
+from ubinascii import hexlify
+import time
+
+class MQTTException(Exception):
+    pass
+
+class MQTTClient:
+
+    def __init__(self, client_id, server, port=1883):
+        self.client_id = client_id
+        self.sock = None
+        self.addr = socket.getaddrinfo(server, port)[0][-1]
+        self.pid = 0
+        self.cb = None
+
+    def _send_str(self, s):
+        self.sock.write(struct.pack("!H", len(s)))
+        self.sock.write(s)
+
+    def _recv_len(self):
+        n = 0
+        sh = 0
+        while 1:
+            b = self.sock.read(1)[0]
+            n |= (b & 0x7f) << sh
+            if not b & 0x80:
+                return n
+            sh += 7
+
+    def set_callback(self, f):
+        self.cb = f
+
+    def connect(self, clean_session=True):
+        self.sock = socket.socket()
+        self.sock.connect(self.addr)
+        msg = bytearray(b"\x10\0\0\x04MQTT\x04\x02\0\0")
+        msg[1] = 10 + 2 + len(self.client_id)
+        msg[9] = clean_session << 1
+        self.sock.write(msg)
+        #print(hex(len(msg)), hexlify(msg, ":"))
+        self._send_str(self.client_id)
+        resp = self.sock.read(4)
+        assert resp[0] == 0x20 and resp[1] == 0x02
+        if resp[3] != 0:
+            raise MQTTException(resp[3])
+        return resp[2] & 1
+
+    def disconnect(self):
+        self.sock.write(b"\xe0\0")
+        self.sock.close()
+
+    def ping(self):
+        self.sock.write(b"\xc0\0")
+        self.sock.close()
+
+    def publish(self, topic, msg, retain=False, qos=0):
+        pkt = bytearray(b"\x30\0\0")
+        pkt[0] |= qos << 1 | retain
+        sz = 2 + len(topic) + len(msg)
+        if qos > 0:
+            sz += 2
+        assert sz <= 16383
+        pkt[1] = (sz & 0x7f) | 0x80
+        pkt[2] = sz >> 7
+        #print(hex(len(pkt)), hexlify(pkt, ":"))
+        self.sock.write(pkt)
+        self._send_str(topic)
+        if qos > 0:
+            self.pid += 1
+            pid = self.pid
+            buf = bytearray(b"\0\0")
+            struct.pack_into("!H", buf, 0, pid)
+            self.sock.write(buf)
+        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
+
+    def subscribe(self, topic, qos=0):
+        assert self.cb is not None, "Subscribe callback is not set"
+        pkt = bytearray(b"\x82\0\0\0")
+        self.pid += 1
+        struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid)
+        #print(hex(len(pkt)), hexlify(pkt, ":"))
+        self.sock.write(pkt)
+        self._send_str(topic)
+        self.sock.write(qos.to_bytes(1))
+        resp = self.sock.read(5)
+        #print(resp)
+        assert resp[0] == 0x90
+        assert resp[2] == pkt[2] and resp[3] == pkt[3]
+        if resp[4] == 0x80:
+            raise MQTTException(resp[4])
+
+    # Wait for a single incoming MQTT message and process it.
+    # Subscribed messages are delivered to a callback previously
+    # set by .set_callback() method. Other (internal) MQTT
+    # messages processed internally.
+    def wait_msg(self):
+        res = self.sock.read(1)
+        if res is None:
+            return None
+        self.sock.setblocking(True)
+        if res == b"":
+            raise OSError(-1)
+        if res == b"\xd0":  # PINGRESP
+            sz = self.sock.read(1)[0]
+            assert sz == 0
+            return None
+        op = res[0]
+        if op & 0xf0 != 0x30:
+            return op
+        sz = self._recv_len()
+        topic_len = self.sock.read(2)
+        topic_len = (topic_len[0] << 8) | topic_len[1]
+        topic = self.sock.read(topic_len)
+        sz -= topic_len + 2
+        if op & 6:
+            pid = self.sock.read(2)
+            pid = pid[0] << 8 | pid[1]
+            sz -= 2
+        msg = self.sock.read(sz)
+        self.cb(topic, msg)
+        if op & 6 == 2:
+            pkt = bytearray(b"\x40\x02\0\0")
+            struct.pack_into("!H", pkt, 2, pid)
+            self.sock.write(pkt)
+        elif op & 6 == 4:
+            assert 0
+
+    # Checks whether a pending message from server is available.
+    # If not, returns immediately with None. Otherwise, does
+    # the same processing as wait_msg.
+    def check_msg(self):
+        self.sock.setblocking(False)
+        return self.wait_msg()