blocks|key|404142|text|不是的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|404143|在蚊子的邮件列表上讨论这个可能更好：https://launchpad.net/~mqtt-users|offset|length|404144|entityMap|0|LINK|mutability|MUTABLE|url|https://launchpad.net/~mqtt-users^0|0|I|X|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

<p>No.</p>

<p>It might be better discussing this on the mosquitto mailing list: <a href="https://launchpad.net/~mqtt-users" rel="nofollow">https://launchpad.net/~mqtt-users</a></p>


blocks|key|404208|text|现在，我使用PHP脚本创建了一个变通方法:它启动蚊子代理，读取输出，如果有人连接或断开连接，它会向代理发送一个包含已连接客户端的xml字符串。(发布的代码稍微简化了一点，因为我在数据库中查询了有关用户的更多信息)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|404209|<?php
require('SAM/php_sam.php');

if+(!$handle+=+popen('mosquitto+2>&1',+'r'))+{

++++die('could+not+start+mosquitto');
}

function+usersToXML($users)+{

++++$xml+=+'<?xml+version="1.0"?><userlist>';
++++foreach($users+as+$user)+{

++++++++$xml+.=+'<user>'+.
++++++++++++'<id><![CDATA['.+$user->id+.']]></id>'+.
++++++++++++'</user>';
++++}

++++$xml+.=+'</userlist>';
++++return+$xml;
}

function+updateBroadcast($users)+{

++++sleep(1);
++++ob_start();
++++$conn+=+new+SAMConnection();
++++$conn->Connect(SAM_MQTT,+array(
++++++++SAM_HOST+=>+'127.0.0.1',
++++++++SAM_PORT+=>+1883
++++));

+++++$conn->Send('topic://broadcast',+(object)array('body'+=>+usersToXML($users)));
+++++$conn->Disconnect();
+++++ob_end_clean();
}

while($line+=+fread($handle,+2096))+{

++++echo+$line;
++++if+(preg_match('/New+client+connected+from+.%2B+as+user_(\d%2B)./',+$line,+$regs))+{

++++++++$user+=+(object)array('id'+=>+$regs[1]);
++++++++$connectedUsers[$user->id]+=+$user;
++++++++updateBroadcast($connectedUsers);

++++}+else+if+(preg_match('/Received+DISCONNECT+from+user_(\d%2B)/',+$line,+$regs)+%7C%7C
++++++++preg_match('/Client+user_(\d%2B)+has+exceeded+timeout,+disconnecting./',+$line,+$regs)+%7C%7C
++++++++preg_match('/Socket+read+error+on+client+user_(\d%2B),+disconnecting./',+$line,+$regs))+{

++++++++if+(isset($connectedUsers[$regs[1]]))+{

++++++++++++unset($connectedUsers[$regs[1]]);
++++++++++++updateBroadcast($connectedUsers);
++++++++}
++++}
}

pclose($handle);
?>|code-block|syntax|javascript|404210|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>well i now created a workaround using a PHP script: it starts the mosquitto broker, reads the output and if someone connects or disconnects it sends an xml string with the connected clients to the broker. (the posted code is a bit simplified as I adiddionally query a database for more information about the user)</p>

<pre><code>&lt;?php
require('SAM/php_sam.php');

if (!$handle = popen('mosquitto 2&gt;&amp;1', 'r')) {

    die('could not start mosquitto');
}

function usersToXML($users) {

    $xml = '&lt;?xml version="1.0"?&gt;&lt;userlist&gt;';
    foreach($users as $user) {

        $xml .= '&lt;user&gt;' .
            '&lt;id&gt;&lt;![CDATA['. $user-&gt;id .']]&gt;&lt;/id&gt;' .
            '&lt;/user&gt;';
    }

    $xml .= '&lt;/userlist&gt;';
    return $xml;
}

function updateBroadcast($users) {

    sleep(1);
    ob_start();
    $conn = new SAMConnection();
    $conn-&gt;Connect(SAM_MQTT, array(
        SAM_HOST =&gt; '127.0.0.1',
        SAM_PORT =&gt; 1883
    ));

     $conn-&gt;Send('topic://broadcast', (object)array('body' =&gt; usersToXML($users)));
     $conn-&gt;Disconnect();
     ob_end_clean();
}

while($line = fread($handle, 2096)) {

    echo $line;
    if (preg_match('/New client connected from .+ as user_(\d+)./', $line, $regs)) {

        $user = (object)array('id' =&gt; $regs[1]);
        $connectedUsers[$user-&gt;id] = $user;
        updateBroadcast($connectedUsers);

    } else if (preg_match('/Received DISCONNECT from user_(\d+)/', $line, $regs) ||
        preg_match('/Client user_(\d+) has exceeded timeout, disconnecting./', $line, $regs) ||
        preg_match('/Socket read error on client user_(\d+), disconnecting./', $line, $regs)) {

        if (isset($connectedUsers[$regs[1]])) {

            unset($connectedUsers[$regs[1]]);
            updateBroadcast($connectedUsers);
        }
    }
}

pclose($handle);
?&gt;
</code></pre>


blocks|key|619913|text|实现这一点的一种方法是让客户端在每次连接代理时发布主题为"status/+client+-id“、有效负载为"1”的消息，并在断开连接时发布有效负载为"0“的消息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|619914|然后在服务器(代理)端，设置另一个客户端订阅主题"status/#"，当它获得任何这样的消息时，将client-id和有效负载(连接或未连接)存储到数据库中。|619915|然后，您可以读取数据库，以确切地知道哪个客户端处于联机或脱机状态。|619916|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

<p>one way to implement this is let the client publish a message with topic "status/client-id" and payload "1" every time when it connects the broker, and with payload "0" when it disconnects.</p>

<p>Then on the server(broker) side, setup another client subscribe to the topic "status/#", when it gets any message like this, store the client-id and payload(connected or not) into database. </p>

<p>then you can read the database to know exactly which client is online or offline. </p>


blocks|key|404288|text|一个很好的解决方法是让客户端(如果可能)定义最后遗嘱和遗嘱(LWT)。您的服务器将订阅一个特殊的主题，其中LWT将发布到该主题，并假定所有客户端都是在线的，除非它们发布到该主题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|404289|MQTT+what+is+the+purpose+or+usage+of+Last+Will+Testament?|offset|length|404290|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/17270863/mqtt-what-is-the-purpose-or-usage-of-last-will-testament^0|0|0|1L|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

<p>A good work-around for this is to have the clients(if possible) define a Last will and testament(LWT). Your server will subscribe to a special topic where the LWT will be published to and assume all clients as online unless they publish to that topic.</p>

<p><a href="https://stackoverflow.com/questions/17270863/mqtt-what-is-the-purpose-or-usage-of-last-will-testament">MQTT what is the purpose or usage of Last Will Testament?</a></p>


blocks|key|404338|text|您可能可以通过BASH命令netstat、grep和awk+(如果需要)获取此信息。如果Mosquitto正在使用端口1883，那么我相信下面的代码会告诉你你想要什么：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|404339|sudo+netstat+%7C+grep+:1883|404340|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

<p>You could presumably get this information via the BASH commands netstat, grep and if necessary awk. If Mosquitto is using port 1883 then the following will tell you what you want I believe:</p>

<p>sudo netstat | grep :1883</p>


blocks|key|620126|text|方法一:在客户端逻辑中进行处理|type|unstyled|depth|inlineStyleRanges|entityRanges|data|620127|正如@user1048839所说，使用客户端的LWT和在线发布消息，在自定义主题上维护客户端状态。下标此主题&自我维护客户列表。|offset|length|style|CODE|620128|如果pub+retain+msg，一次sub将获得客户列表。|620129|方法二:将蚊子代码更改为代理代码|620130|官方代码不支持online_list，|620131|所以我把蚊子打到了1.5.4，添加了2个自定义sys主题：|620132|1.在线列表|620133|mosquitto_sub+-i+DDD+-v+-t+'$SYS/broker/chen_list'
$SYS/broker/chen_list
0+-+CLOUD0_19108
1+-+EEE
2+-+DDD|code-block|syntax|javascript|620134|2.在线/离线事件|620135|mosquitto_sub+-i+DDD+-v+-t+'$SYS/broker/chen_state/#'
$SYS/broker/chen_state/DDD+1
$SYS/broker/chen_state/EEE+1
$SYS/broker/chen_state/CLOUD0_19108+1
$SYS/broker/chen_state/EEE+0
$SYS/broker/chen_state/EEE+1|620136|//如果发布retain消息，则sub此主题可以获取所有客户端的在线状态(在有效负载中)。|620137|在github上测试源代码：|620138|4-online-list|620139|5-online-event|620140|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/eclipse/mosquitto/issues/655|1|https://github.com/yurenchen000/mosquitto/releases/tag/4-online-list|2|https://github.com/yurenchen000/mosquitto/releases/tag/5-online-event^0|0|N|3|0|6|6|0|0|7|B|0|0|0|0|0|0|0|6|6|0|0|0|D|1|0|0|E|2|0^^$0|@$1|2|3|4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1L|8|@$D|1M|E|1N|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1O|8|@$D|1P|E|1Q|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1R|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1S|8|@]|9|@$D|1T|E|1U|1|1V]]|A|$]]|$1|N|3|O|5|6|7|1W|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1X|8|@]|9|@]|A|$]]|$1|R|3|S|5|T|7|1Y|8|@]|9|@]|A|$U|V]]|$1|W|3|X|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|T|7|20|8|@]|9|@]|A|$U|V]]|$1|10|3|11|5|6|7|21|8|@$D|22|E|23|F|G]]|9|@]|A|$]]|$1|12|3|13|5|6|7|24|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|25|8|@]|9|@$D|26|E|27|1|28]]|A|$]]|$1|16|3|17|5|6|7|29|8|@]|9|@$D|2A|E|2B|1|2C]]|A|$]]|$1|18|3|-4|5|6|7|2D|8|@]|9|@]|A|$]]]|19|$1A|$5|1B|1C|1D|A|$1E|1F]]|1G|$5|1B|1C|1D|A|$1E|1H]]|1I|$5|1B|1C|1D|A|$1E|1J]]]]

<h2>method I: handle in client logic</h2>

<p>as @user1048839 says, use client's <code>LWT</code> &amp; online publish msg, 
maintain client status on a custom topic.
subscript this topic &amp; maintain client list self.</p>

<p>if pub <code>retain</code> msg, once sub will get the client list.</p>

<h2>method II: change mosquitto broker code</h2>

<p>official code not support <a href="https://github.com/eclipse/mosquitto/issues/655" rel="nofollow noreferrer">online_list</a>,<br>
so I patched mosquitto 1.5.4, add 2 custom sys topic:</p>

<h3>1. online list</h3>

<pre><code>mosquitto_sub -i DDD -v -t '$SYS/broker/chen_list'
$SYS/broker/chen_list
0 - CLOUD0_19108
1 - EEE
2 - DDD
</code></pre>

<h3>2. online/offline event</h3>

<pre><code>mosquitto_sub -i DDD -v -t '$SYS/broker/chen_state/#'
$SYS/broker/chen_state/DDD 1
$SYS/broker/chen_state/EEE 1
$SYS/broker/chen_state/CLOUD0_19108 1
$SYS/broker/chen_state/EEE 0
$SYS/broker/chen_state/EEE 1
</code></pre>

<p>// if pub <code>retain</code> msg, sub this topic can get all clients online state (in payload).</p>

<p>test source code on github:</p>

<p><a href="https://github.com/yurenchen000/mosquitto/releases/tag/4-online-list" rel="nofollow noreferrer">4-online-list</a></p>

<p><a href="https://github.com/yurenchen000/mosquitto/releases/tag/5-online-event" rel="nofollow noreferrer">5-online-event</a></p>


<p>As a mqtt client connected to mosquitto is it possible to retrieve a list of client IDs who are also  connected to the broker?</p>


Get a list of connected client IDs from MQTT client

作为连接到蚊子的mqtt客户机，是否可以检索也连接到代理的客户机ID的列表？

问从MQTT客户端获取已连接客户端ID的列表
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