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