【MQTT简介】mosquitto-2.0.15-client-sub_client.c源码分析

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#c语言 #windows #前端

/*
Copyright (c) 2009-2012 Roger Light <roger@atchoo.org>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of mosquitto nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef WIN32
#include <unistd.h>
#else
#include <process.h>
#include <winsock2.h>
#define snprintf sprintf_s
#endif

#include <mosquitto.h>

static char **topics = NULL;
static int topic_count = 0;
static int topic_qos = 0;
static char *username = NULL;
static char *password = NULL;
int verbose = 0;
bool quiet = false;

void my_message_callback(void *obj, const struct mosquitto_message *message)
{
//收到消息时，打印
if(verbose){
if(message->payloadlen){
printf("%s %s\n", message->topic, message->payload);
}else{
printf("%s (null)\n", message->topic);
}
fflush(stdout);
}else{
if(message->payloadlen){
printf("%s\n", message->payload);
fflush(stdout);
}
}
}

void my_connect_callback(void *obj, int result)
{
//连接建立后订阅主题
struct mosquitto *mosq = obj;

int i;
if(!result){
for(i=0; i<topic_count; i++){
mosquitto_subscribe(mosq, NULL, topics[i], topic_qos);
}
}else{
switch(result){
case 1:
if(!quiet) fprintf(stderr, "Connection Refused: unacceptable protocol version\n");
break;
case 2:
if(!quiet) fprintf(stderr, "Connection Refused: identifier rejected\n");
break;
case 3:
if(!quiet) fprintf(stderr, "Connection Refused: broker unavailable\n");
break;
case 4:
if(!quiet) fprintf(stderr, "Connection Refused: bad user name or password\n");
break;
case 5:
if(!quiet) fprintf(stderr, "Connection Refused: not authorised\n");
break;
default:
if(!quiet) fprintf(stderr, "Connection Refused: unknown reason\n");
break;
}
}
}

void my_subscribe_callback(void *obj, uint16_t mid, int qos_count, const uint8_t *granted_qos)
{
//打印订阅的相关信息
int i;

if(!quiet) printf("Subscribed (mid: %d): %d", mid, granted_qos[0]);
for(i=1; i<qos_count; i++){
if(!quiet) printf(", %d", granted_qos[i]);
}
if(!quiet) printf("\n");
}

void print_usage(void)
{
//打印mosquitto_sub帮助信息
printf("mosquitto_sub is a simple mqtt client that will subscribe to a single topic and print all messages it receives.\n\n");
printf("Usage: mosquitto_sub [-c] [-h host] [-k keepalive] [-p port] [-q qos] [-v] -t topic ...\n");
printf(" [-i id] [-I id_prefix]\n");
printf(" [-d] [--quiet]\n");
printf(" [-u username [-P password]]\n");
printf(" [--will-topic [--will-payload payload] [--will-qos qos] [--will-retain]]\n\n");
printf(" -c : disable 'clean session' (store subscription and pending messages when client disconnects).\n");
printf(" -d : enable debug messages.\n");
printf(" -h : mqtt host to connect to. Defaults to localhost.\n");
printf(" -i : id to use for this client. Defaults to mosquitto_sub_ appended with the process id.\n");
printf(" -I : define the client id as id_prefix appended with the process id. Useful for when the\n");
printf(" broker is using the clientid_prefixes option.\n");
printf(" -k : keep alive in seconds for this client. Defaults to 60.\n");
printf(" -p : network port to connect to. Defaults to 1883.\n");
printf(" -q : quality of service level to use for the subscription. Defaults to 0.\n");
printf(" -t : mqtt topic to subscribe to. May be repeated multiple times.\n");
printf(" -u : provide a username (requires MQTT 3.1 broker)\n");
printf(" -v : print published messages verbosely.\n");
printf(" -P : provide a password (requires MQTT 3.1 broker)\n");
printf(" --quiet : don't print error messages.\n");
printf(" --will-payload : payload for the client Will, which is sent by the broker in case of\n");
printf(" unexpected disconnection. If not given and will-topic is set, a zero\n");
printf(" length message will be sent.\n");
printf(" --will-qos : QoS level for the client Will.\n");
printf(" --will-retain : if given, make the client Will retained.\n");
printf(" --will-topic : the topic on which to publish the client Will.\n");
printf("\nSee http://mosquitto.org/ for more information.\n\n");
}

int main(int argc, char *argv[])
{
char *id = NULL;
char *id_prefix = NULL;
int i;
char *host = "localhost";
int port = 1883;
int keepalive = 60;
bool clean_session = true;
bool debug = false;
struct mosquitto *mosq = NULL;
int rc;
char hostname[21];
char err[1024];

uint8_t *will_payload = NULL;
long will_payloadlen = 0;
int will_qos = 0;
bool will_retain = false;
char *will_topic = NULL;

for(i=1; i<argc; i++){
if(!strcmp(argv[i], "-p") || !strcmp(argv[i], "--port")){ //-p
if(i==argc-1){
fprintf(stderr, "Error: -p argument given but no port specified.\n\n");
print_usage();
return 1;
}else{
port = atoi(argv[i+1]);
if(port<1 || port>65535){
fprintf(stderr, "Error: Invalid port given: %d\n", port);
print_usage();
return 1;
}
}
i++;
}else if(!strcmp(argv[i], "-c") || !strcmp(argv[i], "--disable-clean-session")){ //-c，在client断开连接之后，仍保持订阅
clean_session = false;
}else if(!strcmp(argv[i], "-d") || !strcmp(argv[i], "--debug")){ //-d
debug = true;
}else if(!strcmp(argv[i], "-h") || !strcmp(argv[i], "--host")){ //-h
if(i==argc-1){
fprintf(stderr, "Error: -h argument given but no host specified.\n\n");
print_usage();
return 1;
}else{
host = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "-i") || !strcmp(argv[i], "--id")){ //-i
if(id_prefix){
fprintf(stderr, "Error: -i and -I argument cannot be used together.\n\n");
print_usage();
return 1;
}
if(i==argc-1){
fprintf(stderr, "Error: -i argument given but no id specified.\n\n");
print_usage();
return 1;
}else{
id = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "-I") || !strcmp(argv[i], "--id-prefix")){ //-I
if(id){
fprintf(stderr, "Error: -i and -I argument cannot be used together.\n\n");
print_usage();
return 1;
}
if(i==argc-1){
fprintf(stderr, "Error: -I argument given but no id prefix specified.\n\n");
print_usage();
return 1;
}else{
id_prefix = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "-k") || !strcmp(argv[i], "--keepalive")){ //-k，keepalive，定义客户端多久向server发送PING以保持连接
if(i==argc-1){
fprintf(stderr, "Error: -k argument given but no keepalive specified.\n\n");
print_usage();
return 1;
}else{
keepalive = atoi(argv[i+1]);
if(keepalive>65535){
fprintf(stderr, "Error: Invalid keepalive given: %d\n", keepalive);
print_usage();
return 1;
}
}
i++;
}else if(!strcmp(argv[i], "-q") || !strcmp(argv[i], "--qos")){ //-q
if(i==argc-1){
fprintf(stderr, "Error: -q argument given but no QoS specified.\n\n");
print_usage();
return 1;
}else{
topic_qos = atoi(argv[i+1]);
if(topic_qos<0 || topic_qos>2){
fprintf(stderr, "Error: Invalid QoS given: %d\n", topic_qos);
print_usage();
return 1;
}
}
i++;
}else if(!strcmp(argv[i], "--quiet")){ //-quiet
quiet = true;
}else if(!strcmp(argv[i], "-t") || !strcmp(argv[i], "--topic")){ //-t，可订阅多个主题
if(i==argc-1){
fprintf(stderr, "Error: -t argument given but no topic specified.\n\n");
print_usage();
return 1;
}else{
topic_count++;
topics = realloc(topics, topic_count*sizeof(char *));
topics[topic_count-1] = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "-u") || !strcmp(argv[i], "--username")){ //-u
if(i==argc-1){
fprintf(stderr, "Error: -u argument given but no username specified.\n\n");
print_usage();
return 1;
}else{
username = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "-v") || !strcmp(argv[i], "--verbose")){ //-v，详细打印消息，格式：topic payload
verbose = 1;
}else if(!strcmp(argv[i], "-P") || !strcmp(argv[i], "--pw")){ //-P
if(i==argc-1){
fprintf(stderr, "Error: -P argument given but no password specified.\n\n");
print_usage();
return 1;
}else{
password = argv[i+1];
}
i++;
}else if(!strcmp(argv[i], "--will-payload")){ //--will-payload
if(i==argc-1){
fprintf(stderr, "Error: --will-payload argument given but no will payload specified.\n\n");
print_usage();
return 1;
}else{
will_payload = (uint8_t *)argv[i+1];
will_payloadlen = strlen((char *)will_payload);
}
i++;
}else if(!strcmp(argv[i], "--will-qos")){ //--will-qos
if(i==argc-1){
fprintf(stderr, "Error: --will-qos argument given but no will QoS specified.\n\n");
print_usage();
return 1;
}else{
will_qos = atoi(argv[i+1]);
if(will_qos < 0 || will_qos > 2){
fprintf(stderr, "Error: Invalid will QoS %d.\n\n", will_qos);
return 1;
}
}
i++;
}else if(!strcmp(argv[i], "--will-retain")){ //--will-retain
will_retain = true;
}else if(!strcmp(argv[i], "--will-topic")){ //--will-topic
if(i==argc-1){
fprintf(stderr, "Error: --will-topic argument given but no will topic specified.\n\n");
print_usage();
return 1;
}else{
will_topic = argv[i+1];
}
i++;
}else{
fprintf(stderr, "Error: Unknown option '%s'.\n",argv[i]);
print_usage();
return 1;
}
}
if(clean_session == false && (id_prefix || !id)){ //设置了-c，就必须使用-i，不能用-I
if(!quiet) fprintf(stderr, "Error: You must provide a client id if you are using the -c option.\n");
return 1;
}
if(id_prefix){
id = malloc(strlen(id_prefix)+10);
if(!id){
if(!quiet) fprintf(stderr, "Error: Out of memory.\n");
return 1;
}
snprintf(id, strlen(id_prefix)+10, "%s%d", id_prefix, getpid());
}else if(!id){
id = malloc(30);
if(!id){
if(!quiet) fprintf(stderr, "Error: Out of memory.\n");
return 1;
}
memset(hostname, 0, 21);
gethostname(hostname, 20);
snprintf(id, 23, "mosq_sub_%d_%s", getpid(), hostname);
}

if(topic_count == 0){
fprintf(stderr, "Error: You must specify a topic to subscribe to.\n");
print_usage();
return 1;
}
if(will_payload && !will_topic){
fprintf(stderr, "Error: Will payload given, but no will topic given.\n");
print_usage();
return 1;
}
if(will_retain && !will_topic){
fprintf(stderr, "Error: Will retain given, but no will topic given.\n");
print_usage();
return 1;
}
if(password && !username){
if(!quiet) fprintf(stderr, "Warning: Not using password since username not set.\n");
}
mosquitto_lib_init(); //任何mosquitto functions之前都必须调用的函数，初始化操作
mosq = mosquitto_new(id, NULL); //新建一个 mosquitto client实例
if(!mosq){
if(!quiet) fprintf(stderr, "Error: Out of memory.\n");
return 1;
}
if(debug){
mosquitto_log_init(mosq, MOSQ_LOG_DEBUG | MOSQ_LOG_ERR | MOSQ_LOG_WARNING
| MOSQ_LOG_NOTICE | MOSQ_LOG_INFO, MOSQ_LOG_STDERR);
}
if(will_topic && mosquitto_will_set(mosq, true, will_topic, will_payloadlen, will_payload, will_qos, will_retain)){
if(!quiet) fprintf(stderr, "Error: Problem setting will.\n");
return 1;
}
if(username && mosquitto_username_pw_set(mosq, username, password)){
if(!quiet) fprintf(stderr, "Error: Problem setting username and password.\n");
return 1;
}
mosquitto_connect_callback_set(mosq, my_connect_callback); //设置client与broker建立连接后所调用的函数
mosquitto_message_callback_set(mosq, my_message_callback); //设置client从broker收到消息后所调用的函数
if(debug){
mosquitto_subscribe_callback_set(mosq, my_subscribe_callback); //设置当broker相应一个订阅请求时所调用的函数
}

rc = mosquitto_connect(mosq, host, port, keepalive, clean_session); //建立连接
if(rc){
if(!quiet){
if(rc == MOSQ_ERR_ERRNO){
#ifndef WIN32
strerror_r(errno, err, 1024);
#else
FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, errno, 0, (LPTSTR)&err, 1024, NULL);
#endif
fprintf(stderr, "Error: %s\n", err);
}else{
fprintf(stderr, "Unable to connect (%d).\n", rc);
}
}
return rc;
}