Fix keepalive handling

Previously the code would send pings only when SocketSelect() would
timeout. This was not working when a client was subscribed to a topic
and would receive periodic messages but wouldn't itself send anything.
This meant that SocketSelect() wouldn't timeout at any point and we
wouldn't execute the check for sending a PINGREQ.

The fix is to do the check for last sent packet before calling
SocketSelect() so that if we haven't been sending anything for a while,
we really send the PINGREQ.

Fixes #10

1 files changed, 13 insertions, 9 deletions

diff --git a/src/client.c b/src/client.c
index b95c8d5..51e86d9 100644
--- a/src/client.c
+++ b/src/client.c
@@ -374,7 +374,20 @@ int MqttClientRunOnce(MqttClient *client, int timeout)
 
         if (SIMPLEQ_EMPTY(&client->sendQueue))
         {
+            int64_t elapsed;
+
             LOG_DEBUG("nothing to write");
+
+            // If there's nothing to write at this point and we haven't sent
+            // any packets in keepalive seconds, we should send a ping.
+
+            elapsed = MqttGetCurrentTime() - client->lastPacketSentTime;
+            if (client->keepAlive > 0 && elapsed >= client->keepAlive*1000)
+            {
+                MqttClientQueueSimplePacket(client, MqttPacketTypePingReq);
+                client->pingSent = 1;
+                events |= EV_WRITE;
+            }
         }
         else
         {
@@ -462,15 +475,6 @@ int MqttClientRunOnce(MqttClient *client, int timeout)
             client->pingSent = 0;
             client->stopped = 1;
         }
-        else if (SIMPLEQ_EMPTY(&client->sendQueue))
-        {
-            int64_t elapsed = MqttGetCurrentTime() - client->lastPacketSentTime;
-            if (elapsed/1000 >= client->keepAlive && client->keepAlive > 0)
-            {
-                MqttClientQueueSimplePacket(client, MqttPacketTypePingReq);
-                client->pingSent = 1;
-            }
-        }
     }
 
     if (client->stopped)