mqtt.lua

@@ -10,52 +10,32 @@ local safeRead = function (conn, n)
 end
 
 local readVarint = function (conn, first_byte)
-    local b, data, err
+    local b, err
     if first_byte == nil then
-        data, err = safeRead(conn, 1)
-        if err ~= nil then
-            return nil, err
-        end
-
-        b = string.byte(data)
+        b, err = safeRead(conn, 1)
     else
         b = first_byte
     end
 
     local n, s = 0, 0
-    while b & 0x80 == 0x80 do
+    while err == nil and b & 0x80 == 0x80 do
         if s > 21 then
-            return nil, "number too large"
+            return 0, "number too large"
         end
 
         n = n + ((b & 0x7F) << s)
         s = s + 7
 
-        data, err = safeRead(conn, 1)
-        if err ~= nil then
-            return nil, err
-        end
+        b, err = safeRead(conn, 1)
+    end
 
-        b = string.byte(data)
+    if err ~= nil then
+        return n, err
     end
 
     return n + (b << s), nil
 end
 
-local encodeVarint = function (n)
-    if n > 268435455 then
-        return nil, "number too large"
-    end
-
-    local data = ""
-    while n > 127 do
-        data = data .. string.char(0x80 | n & 0x7F)
-        n = n >> 7
-    end
-
-    return data .. string.char(n), nil
-end
-
 local MqttClient = {}
 
 function mqtt.open (address, port)
@@ -84,10 +64,6 @@ function MqttClient:new (conn)
 end
 
 function MqttClient:handle ()
-    if not (self.is_connecting or self.is_connected) then
-        return "no connection"
-    end
-
     local data, err = self.conn:safeRead(2)
     if err ~= nil then
         return err
@@ -135,27 +111,12 @@ function MqttClient:handle ()
 
         self.is_connecting = false
         self.is_connected = true
-    elseif ptype & 0xF0 == 0x40 then -- PUBACK
+    elseif ptype == 0x40 then -- PUBACK
         -- TODO
-    elseif ptype & 0xF0 == 0xD0 then -- PINGRESP
+    elseif ptype == 0xD0 then -- PINGRESP
+        -- TODO
+    elseif ptype == 0xE0 then -- DISCONNECT
         -- TODO
-    elseif ptype & 0xF0 == 0xE0 then -- DISCONNECT
-        if ptype ~= 0xE0 then
-            self:disconnect(0x81)
-            return "malformed packet"
-        end
-
-        self.is_connecting = false
-        self.is_connected = false
-
-        if length > 0 then
-            reason, _ = string.unpack("B", data)
-            if reason ~= 0 then
-                return "disconnect with error"
-            end
-        end
-
-        return "disconnect"
     end
 
     return nil
@@ -163,7 +124,7 @@ end
 
 function MqttClient:connect (username, password)
     if self.is_connecting or self.is_connected then
-        return "already connected"
+        return nil
     end
 
     local length = 13
@@ -177,7 +138,11 @@ function MqttClient:connect (username, password)
         flags = flags | 0x40
     end
 
-    local data = string.char(0x10) .. encodeVarint(length) .. string.pack("> s2 B B I2 B s2", "MQTT", 5, flags, 0, 0, "")
+    if length > 127 then
+        return "packet size exceeds current implementation capabilities"
+    end
+
+    local data = string.pack("> B B s2 B B I2 B s2", 0x10, length, "MQTT", 5, flags, 0, 0, "")
     if username ~= nil then
         data = data .. string.pack("> s2", username)
     end
@@ -200,38 +165,9 @@ function MqttClient:connect (username, password)
     return nil
 end
 
-function MqttClient:publish (topic, payload)
-    if not (self.is_connecting or self.is_connected) then
-        return "no connection"
-    end
-
-    if not topic or #topic == 0 then
-        return "topic is required"
-    end
-    if not payload then
-        payload = ""
-    end
-
-    local flags = 0
-    local length = 3 + #topic + #payload
-    local data = string.char(0x30 | flags) .. encodeVarint(length) .. string.pack("> s2 B", topic, 0) .. payload
-
-    local _, err = self.conn:write(data)
-    if err ~= nil then
-        return err
-    end
-
-    local _, err = self.conn:flush()
-    if err ~= nil then
-        return err
-    end
-
-    return nil
-end
-
 function MqttClient:disconnect (reason)
     if not (self.is_connecting or self.is_connected) then
-        return "no connection"
+        return nil
     end
 
     if reason == nil then