Handling MQTT read failure and send buffer length

extras/paho_mqtt_c/MQTTClient.c

@@ -35,7 +35,7 @@ int  sendPacket(MQTTClient* c, int length, Timer* timer)
 
     while (sent < length && !expired(timer))
     {
-        rc = c->ipstack->mqttwrite(c->ipstack, &c->buf[sent], length, left_ms(timer));
+        rc = c->ipstack->mqttwrite(c->ipstack, &c->buf[sent], length - sent, left_ms(timer));
         if (rc < 0)  // there was an error writing the data
             break;
         sent += rc;
@@ -70,7 +70,9 @@ int  decodePacket(MQTTClient* c, int* value, int timeout)
         }
         rc = c->ipstack->mqttread(c->ipstack, &i, 1, timeout);
         if (rc != 1)
+        {
 		    goto exit;
+        }
         *value += (i & 127) * multiplier;
         multiplier *= 128;
     } while ((i & 128) != 0);
@@ -79,6 +81,7 @@ exit:
 }
 
 
+// Return packet type. If no packet avilable, return FAILURE, or READ_ERROR if timeout
 int  readPacket(MQTTClient* c, Timer* timer)
 {
     int rc = FAILURE;
@@ -89,20 +92,19 @@ int  readPacket(MQTTClient* c, Timer* timer)
     /* 1. read the header byte.  This has the packet type in it */
     if (c->ipstack->mqttread(c->ipstack, c->readbuf, 1, left_ms(timer)) != 1)
         goto exit;
-
     len = 1;
     /* 2. read the remaining length.  This is variable in itself */
     decodePacket(c, &rem_len, left_ms(timer));
     len += MQTTPacket_encode(c->readbuf + 1, rem_len); /* put the original remaining length back into the buffer */
-
     /* 3. read the rest of the buffer using a callback to supply the rest of the data */
     if (rem_len > 0 && (c->ipstack->mqttread(c->ipstack, c->readbuf + len, rem_len, left_ms(timer)) != rem_len))
+    {
+        rc = READ_ERROR;
         goto exit;
-
+    }
     header.byte = c->readbuf[0];
     rc = header.bits.type;
 exit:
-    //dmsg_printf("readPacket=%d\r\n", rc);
     return rc;
 }
 
@@ -215,7 +217,7 @@ exit:
 int cycle(MQTTClient* c, Timer* timer)
 {
     // read the socket, see what work is due
-    unsigned short packet_type = readPacket(c, timer);
+    int packet_type = readPacket(c, timer);
 
     int len = 0,
         rc = SUCCESS;
@@ -269,9 +271,15 @@ int  cycle(MQTTClient* c, Timer* timer)
         {
             c->ping_outstanding = 0;
             c->fail_count = 0;
-            }
             break;
         }
+        case READ_ERROR:
+        {
+            c->isconnected = 0; // we simulate a disconnect if reading error
+            rc = DISCONNECTED;  // so that the outer layer will reconnect and recover
+            break;
+        }
+    }
     if (c->isconnected)
         rc = keepalive(c);
 exit:

extras/paho_mqtt_c/MQTTClient.h

@@ -27,7 +27,7 @@
 enum QoS { QOS0, QOS1, QOS2 };
 
 // all failure return codes must be negative
-enum returnCode {DISCONNECTED = -3, BUFFER_OVERFLOW = -2, FAILURE = -1, SUCCESS = 0 };
+enum returnCode {READ_ERROR = -4, DISCONNECTED = -3, BUFFER_OVERFLOW = -2, FAILURE = -1, SUCCESS = 0 };
 
 void NewTimer(Timer*);