Difference between revisions of "MQTT: Arduino Publish di callback"

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-/*
- Publishing in the callback
-  - connects to an MQTT server
-  - subscribes to the topic "inTopic"
-  - when a message is received, republishes it to "outTopic"
-  This example shows how to publish messages within the
-  callback function. The callback function header needs to
-  be declared before the PubSubClient constructor and the
-  actual callback defined afterwards.
-  This ensures the client reference in the callback function
-  is valid.
-*/
-#include <SPI.h>
-#include <Ethernet.h>
-#include <PubSubClient.h>
-// Update these with values suitable for your network.
-byte mac[]    = {  0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED };
-IPAddress ip(192, 168, 0, 4);
-IPAddress server(192, 168, 0, 100);
-// Callback function header
-void callback(char* topic, byte* payload, unsigned int length);
-EthernetClient ethClient;
-PubSubClient client(server, 1883, callback, ethClient);
-// Callback function
-void callback(char* topic, byte* payload, unsigned int length) {
-  // In order to republish this payload, a copy must be made
-  // as the orignal payload buffer will be overwritten whilst
-  // constructing the PUBLISH packet.
-  // Allocate the correct amount of memory for the payload copy
-  byte* p = (byte*)malloc(length);
-  // Copy the payload to the new buffer
-  memcpy(p,payload,length);
-  client.publish("outTopic", p, length);
-  // Free the memory
-  free(p);
-}
-void setup()
-{
-  Ethernet.begin(mac, ip);
-  if (client.connect("arduinoClient")) {
-    client.publish("outTopic","hello world");
-    client.subscribe("inTopic");
-  }
-}
-void loop()
-{
-  client.loop();
-}

Difference between revisions of "MQTT: Arduino Publish di callback"

Revision as of 16:31, 11 May 2018

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