forked from github/esp8266-geigercounter
61 lines
1.5 KiB
C++
61 lines
1.5 KiB
C++
/*
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Publishing in the callback
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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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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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#include <SPI.h>
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#include <Ethernet.h>
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#include <PubSubClient.h>
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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(172, 16, 0, 100);
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IPAddress server(172, 16, 0, 2);
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// Callback function header
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void callback(char* topic, byte* payload, unsigned int length);
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EthernetClient ethClient;
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PubSubClient client(server, 1883, callback, ethClient);
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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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// 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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void setup()
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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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void loop()
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{
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client.loop();
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}
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