Basic client publish example using websockets.
Roger A. Light
4 years ago
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include ../../config.mk
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.PHONY: all
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all : basic-1 basic-websockets-1
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basic-1 : basic-1.o
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${CROSS_COMPILE}${CC} $^ -o $@ ../../lib/libmosquitto.so.${SOVERSION}
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basic-websockets-1 : basic-websockets-1.o
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${CROSS_COMPILE}${CC} $^ -o $@ ../../lib/libmosquitto.so.${SOVERSION}
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basic-1.o : basic-1.c ../../lib/libmosquitto.so.${SOVERSION}
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${CROSS_COMPILE}${CC} -c $< -o $@ -I../../include ${CPPFLAGS} ${CFLAGS}
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basic-websockets-1.o : basic-websockets-1.c ../../lib/libmosquitto.so.${SOVERSION}
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${CROSS_COMPILE}${CC} -c $< -o $@ -I../../include ${CPPFLAGS} ${CFLAGS}
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../../lib/libmosquitto.so.${SOVERSION} :
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$(MAKE) -C ../../lib
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clean :
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-rm -f *.o sub_single sub_multiple
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/*
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* This example shows how to publish messages from outside of the Mosquitto network loop.
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*
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* This is identical to basic-1.c apart from that it uses WebSockets.
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*/
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#include <mosquitto.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#ifndef UNUSED
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# define UNUSED(A) (void)(A)
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#endif
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/* Callback called when the client receives a CONNACK message from the broker. */
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void on_connect(struct mosquitto *mosq, void *obj, int reason_code)
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{
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UNUSED(obj);
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/* Print out the connection result. mosquitto_connack_string() produces an
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* appropriate string for MQTT v3.x clients, the equivalent for MQTT v5.0
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* clients is mosquitto_reason_string().
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*/
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printf("on_connect: %s\n", mosquitto_connack_string(reason_code));
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if(reason_code != 0){
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/* If the connection fails for any reason, we don't want to keep on
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* retrying in this example, so disconnect. Without this, the client
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* will attempt to reconnect. */
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mosquitto_disconnect(mosq);
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}
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/* You may wish to set a flag here to indicate to your application that the
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* client is now connected. */
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}
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/* Callback called when the client knows to the best of its abilities that a
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* PUBLISH has been successfully sent. For QoS 0 this means the message has
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* been completely written to the operating system. For QoS 1 this means we
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* have received a PUBACK from the broker. For QoS 2 this means we have
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* received a PUBCOMP from the broker. */
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void on_publish(struct mosquitto *mosq, void *obj, int mid)
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{
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UNUSED(mosq);
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UNUSED(obj);
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printf("Message with mid %d has been published.\n", mid);
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}
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int get_temperature(void)
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{
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sleep(1); /* Prevent a storm of messages - this pretend sensor works at 1Hz */
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return (int)random()%100;
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}
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/* This function pretends to read some data from a sensor and publish it.*/
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void publish_sensor_data(struct mosquitto *mosq)
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{
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char payload[20];
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int temp;
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int rc;
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/* Get our pretend data */
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temp = get_temperature();
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/* Print it to a string for easy human reading - payload format is highly
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* application dependent. */
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snprintf(payload, sizeof(payload), "%d", temp);
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/* Publish the message
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* mosq - our client instance
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* *mid = NULL - we don't want to know what the message id for this message is
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* topic = "example/temperature" - the topic on which this message will be published
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* payloadlen = strlen(payload) - the length of our payload in bytes
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* payload - the actual payload
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* qos = 2 - publish with QoS 2 for this example
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* retain = false - do not use the retained message feature for this message
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*/
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rc = mosquitto_publish(mosq, NULL, "example/temperature", (int)strlen(payload), payload, 2, false);
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if(rc != MOSQ_ERR_SUCCESS){
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fprintf(stderr, "Error publishing: %s\n", mosquitto_strerror(rc));
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}
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}
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int main(int argc, char *argv[])
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{
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struct mosquitto *mosq;
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int rc;
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UNUSED(argc);
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UNUSED(argv);
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/* Required before calling other mosquitto functions */
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mosquitto_lib_init();
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/* Create a new client instance.
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* id = NULL -> ask the broker to generate a client id for us
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* clean session = true -> the broker should remove old sessions when we connect
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* obj = NULL -> we aren't passing any of our private data for callbacks
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*/
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mosq = mosquitto_new(NULL, true, NULL);
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if(mosq == NULL){
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fprintf(stderr, "Error: Out of memory.\n");
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return 1;
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}
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mosquitto_int_option(mosq, MOSQ_OPT_TRANSPORT, MOSQ_T_WEBSOCKETS);
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/* Configure callbacks. This should be done before connecting ideally. */
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mosquitto_connect_callback_set(mosq, on_connect);
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mosquitto_publish_callback_set(mosq, on_publish);
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/* Connect to test.mosquitto.org on port 1883, with a keepalive of 60 seconds.
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* This call makes the socket connection only, it does not complete the MQTT
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* CONNECT/CONNACK flow, you should use mosquitto_loop_start() or
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* mosquitto_loop_forever() for processing net traffic. */
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rc = mosquitto_connect(mosq, "test.mosquitto.org", 8080, 60);
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if(rc != MOSQ_ERR_SUCCESS){
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mosquitto_destroy(mosq);
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fprintf(stderr, "Error: %s\n", mosquitto_strerror(rc));
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return 1;
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}
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/* Run the network loop in a background thread, this call returns quickly. */
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rc = mosquitto_loop_start(mosq);
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if(rc != MOSQ_ERR_SUCCESS){
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mosquitto_destroy(mosq);
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fprintf(stderr, "Error: %s\n", mosquitto_strerror(rc));
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return 1;
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}
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/* At this point the client is connected to the network socket, but may not
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* have completed CONNECT/CONNACK.
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* It is fairly safe to start queuing messages at this point, but if you
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* want to be really sure you should wait until after a successful call to
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* the connect callback.
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* In this case we know it is 1 second before we start publishing.
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*/
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while(1){
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publish_sensor_data(mosq);
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}
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mosquitto_lib_cleanup();
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return 0;
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}
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