部署EMQX集群

一 . 环境说明

操作系统 : CentOS7

集群节点 : 

172.18.0.231 集群节点1
172.18.0.232 集群节点2
172.18.0.233 集群节点3

EMQ X Broker版本 : 4.1.0

集群发现策略 : etcd

认证方式 : PostgreSQL方式 

密码加密 : SHA-265

SSL双向认证 : 启用

二 . 准备工作

准备etcd集群 , 可参考 : https://www.cnblogs.com/kreo/p/13155893.html

准备SSL证书 , 可参考 : https://www.cnblogs.com/kreo/p/13203973.html

三 . 下载EMQX

官网下载 : https://www.emqx.io/cn/products/broker

百度网盘下载 : 

链接：https://pan.baidu.com/s/1mvs4M76cWeQh7VmkQXx9EA 
提取码：zfb5

四 . 解压安装包

注意 : 本文都采用root用户进行安装 , 如果需要切换其他用户 , 也可以正常运行(注意权限问题)

#解压
unzip emqx-centos7-v4.1.0.zip
#可以移到任何你想移动到的目录 , 本例子是移动到了/home下 , 即安装目录为 /home/emqx
mv emqx /home/

PS : ***本文都是使用 /home/emqx 作为 ${emqx_home} 进行处理 ,如需改变 , 则需要修改相应的配置文件***

五. 修改主配置文件

主配置文件路径 : /home/emqx/etc/emqx.conf

主要修改下面几部分 : 

1 . 节点名称(node.name)

2 . PostgreSQL认证

3 . SSL认证

4 . etcd认证开启

下面是我配置文件全文 , 可直接拿过去使用 , 需要修改部分我标了红色 : 

cluster.name = wanmaemqxcl
cluster.proto_dist = inet_tcp
cluster.discovery = etcd
cluster.autoheal = on
cluster.autoclean = 5m
#其他节点的server也可能要改
cluster.etcd.server = http://127.0.0.1:2379
cluster.etcd.prefix = emqxcl
cluster.etcd.node_ttl = 1m
#其他节点的node.name要改
node.name = emqx@172.18.0.231
node.cookie = emqxsecretcookie
node.data_dir = data
node.global_gc_interval = 15m
node.crash_dump = log/crash.dump
node.dist_listen_min = 6369
node.dist_listen_max = 6369
rpc.mode = async
rpc.async_batch_size = 256
rpc.tcp_server_port = 5369
rpc.tcp_client_port = 5369
rpc.connect_timeout = 5s
rpc.send_timeout = 5s
rpc.authentication_timeout = 5s
rpc.call_receive_timeout = 15s
rpc.socket_keepalive_idle = 900s
rpc.socket_keepalive_interval = 75s
rpc.socket_keepalive_count = 9
rpc.socket_sndbuf = 1MB
rpc.socket_recbuf = 1MB
rpc.socket_buffer = 1MB
log.to = both
log.level = notice
log.dir = log
log.file = emqx.log
#log.chars_limit = 8192
log.rotation = on
log.rotation.size = 10MB
log.rotation.count = 5
#log.info.file  = info.log
log.error.file = error.log
#log.sync_mode_qlen = 100
#log.drop_mode_qlen = 3000
#log.flush_qlen = 8000
#log.overload_kill = on
#log.overload_kill_qlen = 20000
#log.overload_kill_mem_size = 30MB
#log.overload_kill_restart_after = 5s
#log.burst_limit = 20000, 1s
allow_anonymous = false
acl_nomatch = allow
acl_file = etc/acl.conf
enable_acl_cache = on
acl_cache_max_size = 32
acl_cache_ttl = 1m
acl_deny_action = ignore
flapping_detect_policy = 30, 1m, 5m
mqtt.max_packet_size = 1MB
mqtt.max_clientid_len = 65535
mqtt.max_topic_levels = 0
mqtt.max_qos_allowed = 2
mqtt.max_topic_alias = 65535
mqtt.retain_available = true
mqtt.wildcard_subscription = true
mqtt.shared_subscription = true
mqtt.ignore_loop_deliver = false
mqtt.strict_mode = false
zone.external.idle_timeout = 15s
zone.external.enable_acl = on
zone.external.enable_ban = on
zone.external.enable_stats = on
zone.external.acl_deny_action = ignore
#可根据实际情况修改
zone.external.force_gc_policy = 32000|32MB
zone.external.keepalive_backoff = 0.75
zone.external.max_subscriptions = 0
zone.external.upgrade_qos = off
zone.external.max_inflight = 32
zone.external.retry_interval = 30s
zone.external.max_awaiting_rel = 100
zone.external.await_rel_timeout = 300s
zone.external.session_expiry_interval = 2h
zone.external.max_mqueue_len = 1000
zone.external.mqueue_priorities = none
zone.external.mqueue_default_priority = highest
zone.external.mqueue_store_qos0 = true
zone.external.enable_flapping_detect = off
zone.external.use_username_as_clientid = false
zone.external.ignore_loop_deliver = false
zone.external.strict_mode = false
zone.internal.allow_anonymous = true
zone.internal.enable_stats = on
zone.internal.enable_acl = off
zone.internal.acl_deny_action = ignore
zone.internal.max_subscriptions = 0
zone.internal.max_inflight = 128
zone.internal.max_awaiting_rel = 1000
zone.internal.max_mqueue_len = 10000
zone.internal.mqueue_store_qos0 = true
zone.internal.enable_flapping_detect = off
zone.internal.ignore_loop_deliver = false
zone.internal.strict_mode = false
zone.internal.bypass_auth_plugins = true
listener.tcp.external = 0.0.0.0:1883
listener.tcp.external.acceptors = 8
listener.tcp.external.max_connections = 1024000
listener.tcp.external.max_conn_rate = 1000
listener.tcp.external.active_n = 100
listener.tcp.external.zone = external
listener.tcp.external.access.1 = allow all
listener.tcp.external.backlog = 1024
listener.tcp.external.send_timeout = 15s
listener.tcp.external.send_timeout_close = on
listener.tcp.external.nodelay = true
listener.tcp.external.reuseaddr = true
listener.tcp.internal = 127.0.0.1:11883
listener.tcp.internal.acceptors = 4
listener.tcp.internal.max_connections = 1024000
listener.tcp.internal.max_conn_rate = 1000
listener.tcp.internal.active_n = 1000
listener.tcp.internal.zone = internal
listener.tcp.internal.backlog = 512
listener.tcp.internal.send_timeout = 5s
listener.tcp.internal.send_timeout_close = on
listener.tcp.internal.recbuf = 64KB
listener.tcp.internal.sndbuf = 64KB
listener.tcp.internal.nodelay = false
listener.tcp.internal.reuseaddr = true
listener.ssl.external = 8883
listener.ssl.external.acceptors = 16
listener.ssl.external.max_connections = 102400
listener.ssl.external.max_conn_rate = 500
listener.ssl.external.active_n = 100
listener.ssl.external.zone = external
listener.ssl.external.access.1 = allow all
listener.ssl.external.tls_versions = tlsv1.3,tlsv1.2,tlsv1.1,tlsv1
listener.ssl.external.handshake_timeout = 15s
#证书文件要放到/home/emqx/etc/certs目录下
listener.ssl.external.keyfile = etc/certs/server.key
listener.ssl.external.certfile = etc/certs/server.pem
listener.ssl.external.cacertfile = etc/certs/ca.pem
listener.ssl.external.verify = verify_peer
listener.ssl.external.fail_if_no_peer_cert = true
listener.ssl.external.ciphers = ECDHE-ECDSA-AES256-GCM-SHA384,ECDHE-RSA-AES256-GCM-SHA384,ECDHE-ECDSA-AES256-SHA384,ECDHE-RSA-AES256-SHA384,ECDHE-ECDSA-DES-CBC3-SHA,ECDH-ECDSA-AES256-GCM-SHA384,ECDH-RSA-AES256-GCM-SHA384,ECDH-ECDSA-AES256-SHA384,ECDH-RSA-AES256-SHA384,DHE-DSS-AES256-GCM-SHA384,DHE-DSS-AES256-SHA256,AES256-GCM-SHA384,AES256-SHA256,ECDHE-ECDSA-AES128-GCM-SHA256,ECDHE-RSA-AES128-GCM-SHA256,ECDHE-ECDSA-AES128-SHA256,ECDHE-RSA-AES128-SHA256,ECDH-ECDSA-AES128-GCM-SHA256,ECDH-RSA-AES128-GCM-SHA256,ECDH-ECDSA-AES128-SHA256,ECDH-RSA-AES128-SHA256,DHE-DSS-AES128-GCM-SHA256,DHE-DSS-AES128-SHA256,AES128-GCM-SHA256,AES128-SHA256,ECDHE-ECDSA-AES256-SHA,ECDHE-RSA-AES256-SHA,DHE-DSS-AES256-SHA,ECDH-ECDSA-AES256-SHA,ECDH-RSA-AES256-SHA,AES256-SHA,ECDHE-ECDSA-AES128-SHA,ECDHE-RSA-AES128-SHA,DHE-DSS-AES128-SHA,ECDH-ECDSA-AES128-SHA,ECDH-RSA-AES128-SHA,AES128-SHA
#listener.ssl.external.psk_ciphers = PSK-AES128-CBC-SHA,PSK-AES256-CBC-SHA,PSK-3DES-EDE-CBC-SHA,PSK-RC4-SHA
listener.ssl.external.reuseaddr = true
listener.ws.external = 8083
listener.ws.external.mqtt_path = /mqtt
listener.ws.external.acceptors = 4
listener.ws.external.max_connections = 102400
listener.ws.external.max_conn_rate = 1000
listener.ws.external.active_n = 100
listener.ws.external.zone = external
listener.ws.external.access.1 = allow all
listener.ws.external.verify_protocol_header = on
listener.ws.external.backlog = 1024
listener.ws.external.send_timeout = 15s
listener.ws.external.send_timeout_close = on
listener.ws.external.nodelay = true
listener.wss.external = 8084
listener.wss.external.mqtt_path = /mqtt
listener.wss.external.acceptors = 4
listener.wss.external.max_connections = 16
listener.wss.external.max_conn_rate = 1000
listener.wss.external.active_n = 100
listener.wss.external.zone = external
listener.wss.external.access.1 = allow all
listener.wss.external.verify_protocol_header = on
listener.wss.external.keyfile = etc/certs/server.key
listener.wss.external.certfile = etc/certs/server.pem
listener.wss.external.ciphers = ECDHE-ECDSA-AES256-GCM-SHA384,ECDHE-RSA-AES256-GCM-SHA384,ECDHE-ECDSA-AES256-SHA384,ECDHE-RSA-AES256-SHA384,ECDHE-ECDSA-DES-CBC3-SHA,ECDH-ECDSA-AES256-GCM-SHA384,ECDH-RSA-AES256-GCM-SHA384,ECDH-ECDSA-AES256-SHA384,ECDH-RSA-AES256-SHA384,DHE-DSS-AES256-GCM-SHA384,DHE-DSS-AES256-SHA256,AES256-GCM-SHA384,AES256-SHA256,ECDHE-ECDSA-AES128-GCM-SHA256,ECDHE-RSA-AES128-GCM-SHA256,ECDHE-ECDSA-AES128-SHA256,ECDHE-RSA-AES128-SHA256,ECDH-ECDSA-AES128-GCM-SHA256,ECDH-RSA-AES128-GCM-SHA256,ECDH-ECDSA-AES128-SHA256,ECDH-RSA-AES128-SHA256,DHE-DSS-AES128-GCM-SHA256,DHE-DSS-AES128-SHA256,AES128-GCM-SHA256,AES128-SHA256,ECDHE-ECDSA-AES256-SHA,ECDHE-RSA-AES256-SHA,DHE-DSS-AES256-SHA,ECDH-ECDSA-AES256-SHA,ECDH-RSA-AES256-SHA,AES256-SHA,ECDHE-ECDSA-AES128-SHA,ECDHE-RSA-AES128-SHA,DHE-DSS-AES128-SHA,ECDH-ECDSA-AES128-SHA,ECDH-RSA-AES128-SHA,AES128-SHA
listener.wss.external.backlog = 1024
listener.wss.external.send_timeout = 15s
listener.wss.external.send_timeout_close = on
modules.loaded_file = data/loaded_modules
module.presence.qos = 1
plugins.etc_dir = etc/plugins/
plugins.loaded_file = data/loaded_plugins
plugins.expand_plugins_dir = plugins/
broker.sys_interval = 1m
broker.sys_heartbeat = 30s
broker.session_locking_strategy = quorum
broker.shared_subscription_strategy = random
broker.shared_dispatch_ack_enabled = false
broker.route_batch_clean = off
sysmon.long_gc = 0
sysmon.long_schedule = 240ms
sysmon.large_heap = 8MB
sysmon.busy_port = false
sysmon.busy_dist_port = true
os_mon.cpu_check_interval = 60s
os_mon.cpu_high_watermark = 80%
os_mon.cpu_low_watermark = 60%
os_mon.mem_check_interval = 60s
os_mon.sysmem_high_watermark = 70%
os_mon.procmem_high_watermark = 5%
vm_mon.check_interval = 30s
vm_mon.process_high_watermark = 80%
vm_mon.process_low_watermark = 60%

六 . 开启PostgreSQL认证

1 . 新建PostgreSQL数据库 , 并新建表(为了和业务结合, 我改了官方的表名和部分结构)

新建数据库 : mqttconfig
用户名 : mqtt
密码 : 123456

新建用户表

CREATE TABLE "public"."ct_sys_emqx_user" (
  "id" int4 NOT NULL,
  "is_superuser" bool NOT NULL,
  "username" varchar(100) COLLATE "pg_catalog"."default" NOT NULL,
  "password" varchar(255) COLLATE "pg_catalog"."default" NOT NULL,
  "salt" varchar(255) COLLATE "pg_catalog"."default",
  "enable" int2 NOT NULL DEFAULT 1,
  "add_user" varchar(64) COLLATE "pg_catalog"."default",
  "add_time" timestamp(6),
  "lm_user" varchar(64) COLLATE "pg_catalog"."default",
  "lm_time" timestamp(6),
  CONSTRAINT "ct_sys_emqx_user_pkey" PRIMARY KEY ("id")
);
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."id" IS '主键ID';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."is_superuser" IS '是否超级用户';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."username" IS '用户名';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."password" IS '密码';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."salt" IS '盐值';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."enable" IS '禁用0启用1';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."add_user" IS '创建人';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."add_time" IS '创建时间';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."lm_user" IS '修改人';
COMMENT ON COLUMN "public"."ct_sys_emqx_user"."lm_time" IS '修改时间';
COMMENT ON TABLE "public"."ct_sys_emqx_user" IS 'EMQX用户表';

新建ACL表(访问控制表)

CREATE TABLE "public"."ct_sys_emqx_acl" (
  "id" int4 NOT NULL,
  "allow" int4 NOT NULL,
  "ipaddr" varchar(60) COLLATE "pg_catalog"."default",
  "username" varchar(100) COLLATE "pg_catalog"."default",
  "clientid" varchar(100) COLLATE "pg_catalog"."default",
  "access" int4,
  "topic" varchar(100) COLLATE "pg_catalog"."default",
  "level" int4 NOT NULL DEFAULT 100,
  "enable" int2 NOT NULL DEFAULT 1,
  "add_user" varchar(64) COLLATE "pg_catalog"."default",
  "add_time" timestamp(6),
  "lm_user" varchar(64) COLLATE "pg_catalog"."default",
  "lm_time" timestamp(6),
  CONSTRAINT "ct_sys_emqx_acl_pkey" PRIMARY KEY ("id")
);
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."id" IS '主键ID';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."allow" IS '禁止0允许1';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."ipaddr" IS 'IP地址';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."username" IS '用户名($all代表全部用户)';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."clientid" IS '客户端';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."access" IS '操作:订阅1发布2全部3';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."topic" IS '控制的主题(允许占位符)';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."level" IS '等级,越高越优先';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."enable" IS '禁用0启用1';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."add_user" IS '创建人';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."add_time" IS '创建时间';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."lm_user" IS '修改人';
COMMENT ON COLUMN "public"."ct_sys_emqx_acl"."lm_time" IS '修改时间';

添加相应数据到用户表

注意 : password填入的是SHA-256加密后的字符串 , SHA-256加密方法参考:

public static String encryptSHA256(String content) {
    try {
        MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
        return Hex.encodeHexString(messageDigest.digest(content.getBytes("UTF-8")));
    } catch (UnsupportedEncodingException | NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return null;
}

PS : 密码的Hex一定要用全小写字符 , 全大写的经测试无效 , 所以采用Hex.encodeHexString方法 , 该方法生成全小写的Hex字符串

2 . 修改emqx_auth_pgsql插件配置文件

配置文件路径 : /home/emqx/etc/plugins/emqx_auth_pgsql.conf

auth.pgsql.server = 2.18.0.97:5432
auth.pgsql.pool = 8
auth.pgsql.username = mqtt
auth.pgsql.password = 123456
auth.pgsql.database = mqttconfig
auth.pgsql.encoding = utf8
auth.pgsql.ssl = false
auth.pgsql.auth_query = select password from ct_sys_emqx_user where username = '%u' and enable = 1 limit 1
auth.pgsql.password_hash = sha256
auth.pgsql.super_query = select is_superuser from ct_sys_emqx_user where username = '%u' and enable = 1 limit 1
auth.pgsql.acl_query = select allow, ipaddr, username, clientid, access, topic from ct_sys_emqx_acl where enable = 1 and (ipaddr = '%a' or username = '%u' or username = '$all' or clientid = '%c') order by level desc

3. 修改插件加载配置

修改插件加载配置 : /home/emqx/data/loaded_plugins

下面加上一行 : {emqx_auth_pgsql,true}.

注意有个点 .

完成配置文件如下 : (你如果已经加载了其他插件 , 则可能会不同)

{emqx_management, true}.
{emqx_recon, true}.
{emqx_retainer, true}.
{emqx_dashboard, true}.
{emqx_rule_engine, true}.
{emqx_bridge_mqtt, false}.
{emqx_auth_pgsql , true}.

也可能这样 : 

emqx_management.
emqx_recon.
emqx_retainer.
emqx_dashboard.
emqx_rule_engine.
emqx_auth_pgsql.

两种配置效果一样.

通过命令方式动态加载插件 : 

# ** 需要在emqx启动后
# 使用命令 加载插件
/home/emqx/bin/emqx_ctl plugins load emqx_auth_pgsql

七 . 启动/关闭 EMQX

1 .  改变当前环境变量(.bash_profile) , 把/home/emqx/bin 加入PATH中 (非必须)

2 . 启动关闭脚本

#启动脚本
/home/emqx/bin/emqx start

#关闭脚本
/home/emqx/bin/emqx stop

#查看启动状态
/home/emqx/bin/emqx_ctl status

八 . 部署其他集群环境

改变第四步中的 主配置文件中的 node.name 和 cluster.etcd.server(根据情况) , 其他全部按照 三 ~ 七 步骤进行部署

九 . 其他常用命令

# 重启EMQX
emqx restart

#///启动关闭插件 
# 查看插件加载情况
emqx_ctl plugins list  # Show loaded plugins
# 加载插件
emqx_ctl plugins load <Plugin> 
# 取消加载插件
emqx_ctl plugins unload <Plugin>
# 重新加载插件
emqx_ctl plugins reload <Plugin>

十 . WEB管理端(DashBoard)

随便打开集群某一台的18083端口即可访问

http://172.18.0.231:18083

默认用户名 : admin

默认密码 : public (注意修改)

里面可以查看一些集群监控信息

注意 : 此DashBorad只作为监控使用 , 不要用作管理(比如加载插件) , 否则可能出现不可预计的后果

十一 . nginx代理

使用nginx代理即可实现集群的负载均衡

首先nginx必须加载with-stream和with-stream_ssl_module模块

具体nginx安装可参考 : https://www.cnblogs.com/kreo/p/4378086.html

注意 : 下面配置需要放在 stream 块中

log_format proxy '$remote_addr [$time_local] '
                 '$protocol $status $bytes_sent $bytes_received '
                 '$session_time "$upstream_addr" '
                 '"$upstream_bytes_sent" "$upstream_bytes_received" "$upstream_connect_time"';

upstream emqx_servers {
    zone emqx_servers 64k;
    hash $remote_addr;
    server 172.18.0.231:1883 max_fails=2 fail_timeout=30s weight=100;
    server 172.18.0.232:1883 max_fails=2 fail_timeout=30s weight=100;
    server 172.18.0.233:1883 max_fails=2 fail_timeout=30s weight=100;
}

server {
    listen 8883 ssl;    
    proxy_pass emqx_servers;
    proxy_buffer_size 4k;
    ssl_handshake_timeout 15s;
    # 下面2个模块在nginx商业授权中 , 土豪可以打开
    # status_zone emqx_servers;
    # health_check;
    # 证书需要复制过来放入相应的目录中
    ssl_certificate     /usr/local/nginx/conf/certs/emqx/client.pem;
    ssl_certificate_key /usr/local/nginx/conf/certs/emqx/client.key;

    access_log    /u01/log/nginx/emqx.access.log proxy;
    error_log    /u01/log/nginx/emqx.error.log;
}

假设nginx服务器所在的IP是 : 172.18.0.97

那么 , 统一可以使用 ssl://172.18.0.97:8883 进行访问

十二 . JAVA访问例子

创建连接:

package test.mqtt;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.internal.security.SSLSocketFactoryFactory;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import java.util.Properties;

/**
 * @author kreo
 * @description
 * @date 2020-6-23 23:15:16
 */
public class MqttConnection {
    private final static String broker = "ssl://172.18.0.97:8883";
    private final static String clientId = "LOCAL_JAVA_CLIENT";
    private final static MemoryPersistence persistence = new MemoryPersistence();

    private static MqttClient client;

    public static MqttClient getClient() {
        try {
            if (client == null) {
                client = new MqttClient(broker, clientId, persistence);

                // MQTT 连接选项
                MqttConnectOptions connOptions = new MqttConnectOptions();
                connOptions.setUserName("guest");
                connOptions.setPassword("123456".toCharArray());
                Properties sslProperties = new Properties();
                sslProperties.put(SSLSocketFactoryFactory.KEYSTORE, "/usr/var/certs/client.jks");
                sslProperties.put(SSLSocketFactoryFactory.KEYSTOREPWD, "client.wanmagroup.com");
                sslProperties.put(SSLSocketFactoryFactory.KEYSTORETYPE, "JKS");

                sslProperties.put(SSLSocketFactoryFactory.TRUSTSTORE, "/usr/var/certs/ca.jks");
                sslProperties.put(SSLSocketFactoryFactory.TRUSTSTOREPWD, "wanmagroup.com");
                sslProperties.put(SSLSocketFactoryFactory.TRUSTSTORETYPE, "JKS");
                sslProperties.put(SSLSocketFactoryFactory.CLIENTAUTH, true);

                connOptions.setSSLProperties(sslProperties);
                // 保留会话
                connOptions.setCleanSession(true);

                // 设置回调
                client.setCallback(new OnMessageCallback());

                // 建立连接
                System.out.println("尝试建立连接... Broker >> " + broker);
                client.connect(connOptions);

                System.out.println("建立连接成功");
            }
        } catch (MqttException me) {
            System.out.println("原因代码 " + me.getReasonCode());
            System.out.println("信息 " + me.getMessage());
            System.out.println("LOC " + me.getLocalizedMessage());
            System.out.println("原因 " + me.getCause());
            me.printStackTrace();
        }
        return client;
    }

    public static void close() {
        try {
            client.disconnect();
            System.out.println("断开连接");
            client.close();
            System.out.println("连接关闭");
        } catch (MqttException me) {
            System.out.println("原因代码 " + me.getReasonCode());
            System.out.println("信息 " + me.getMessage());
            System.out.println("LOC " + me.getLocalizedMessage());
            System.out.println("原因 " + me.getCause());
            me.printStackTrace();
        }

    }
}

订阅和发布例子:

package test.mqtt;

import com.wanma.framework.util.IDate;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;

import java.io.UnsupportedEncodingException;

/**
 * @author kreo
 * @description
 * @date 2020-6-23 13:45:22
 */
public class MqttClientHandle {
    // private final static String subTopic = "/home/kreo/testsub";
    private final static String pubTopic = "/home/kreo/testpub";

    public MqttClientHandle() {

    }

    public static void subscribe() {
        try {
            // MqttAsyncConnection.getClient().subscribe(pubTopic, 0);
            MqttConnection.getClient().subscribe(pubTopic, 2);
        } catch (MqttException me) {
            System.out.println("原因代码 " + me.getReasonCode());
            System.out.println("信息 " + me.getMessage());
            System.out.println("LOC " + me.getLocalizedMessage());
            System.out.println("原因 " + me.getCause());
            me.printStackTrace();
        }
    }

    public static void publish(int qos) {
        try {
            String content = "发送:" + IDate.getNowMillis();
            MqttMessage message = new MqttMessage();
            message.setQos(qos);
            message.setPayload(content.getBytes("UTF-8"));
            MqttConnection.getClient().publish(pubTopic, message);
        } catch (MqttException me) {
            System.out.println("原因代码 " + me.getReasonCode());
            System.out.println("信息 " + me.getMessage());
            System.out.println("LOC " + me.getLocalizedMessage());
            System.out.println("原因 " + me.getCause());
            me.printStackTrace();
        } catch (UnsupportedEncodingException ue) {
            ue.printStackTrace();
        }
    }


    // public static

    public static void main(String[] args) {
        // 订阅
        subscribe();

        //发布
        publish(0);
        //publish(1);
        //publish(2);
    }
}

十三 . 其他特别知识点

1 . 消息的QOS可能会降级 , 比如使用QOS=2发布 , 但是接收方却使用QOS = 0进行接收 , 那么消息就会降级成为QOS0被接收方接收