MQTT with curl

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <title>MQTT with curl</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type"> <link rel="stylesheet" type="text/css" href="/curl.css"> <link rel="shortcut icon" href="/favicon.ico"> <link rel="icon" href="/logo/curl-symbol.svg" type="image/svg+xml"> <link rel="alternate" type="application/rss+xml" title="cURL Releases" href="https://github.com/curl/curl/releases.atom"> </head> <body> <div class="main"> <div class="menu"> <a href="/docs/" class="menuitem" title="Documentation Overview">Docs Overview</a> <div class="dropdown"> <a class="dropbtn" href="/docs/projdocs.html">Project</a> <div class="dropdown-content"> <a href="/docs/bugbounty.html">Bug Bounty</a> <a href="/docs/bugs.html">Bug Report</a> <a href="/docs/code-of-conduct.html">Code of conduct</a> <a href="/docs/libs.html">Dependencies</a> <a href="/donation.html">Donate</a> <a href="/docs/faq.html">FAQ</a> <a href="/docs/features.html">Features</a> <a href="/docs/governance.html">Governance</a> <a href="/docs/history.html">History</a> <a href="/docs/install.html">Install</a> <a href="/docs/knownbugs.html">Known Bugs</a> <a href="/logo/">Logo</a> <a href="/docs/todo.html">TODO</a> <a href="/about.html">website Info</a> </div> </div> <div class="dropdown"> <a class="dropbtn" href="/docs/protdocs.html">Protocols</a> <div class="dropdown-content"> <a href="/docs/caextract.html">CA Extract</a> <a href="/docs/http-cookies.html">HTTP cookies</a> <a href="/docs/http3.html">HTTP/3</a> <a href="/docs/mqtt.html">MQTT</a> <a href="/docs/sslcerts.html">SSL certs</a> <a href="/docs/ssl-compared.html">SSL libs compared</a> <a href="/docs/url-syntax.html">URL syntax</a> <a href="/docs/websocket.html">WebSocket</a> </div> </div> <div class="dropdown"> <a class="dropbtn" href="/docs/reldocs.html">Releases</a> <div class="dropdown-content"> <a href="/ch/">Changelog</a> <a href="/docs/security.html">curl CVEs</a> <a href="/docs/releases.html">Release Table</a> <a href="/docs/versions.html">Version Numbering</a> <a href="/docs/vulnerabilities.html">Vulnerabilities</a> </div> </div> <div class="dropdown"> <a class="dropbtn" href="/docs/tooldocs.html">Tool</a> <div class="dropdown-content"> <a href="/docs/comparison-table.html">Comparison Table</a> <a href="/docs/manpage.html">curl man page</a> <a href="/docs/httpscripting.html">HTTP Scripting</a> <a href="/docs/mk-ca-bundle.html">mk-ca-bundle</a> <a href="/docs/tutorial.html">Tutorial</a> <a href="optionswhen.html">When options were added</a> </div> </div> <div class="dropdown"> <a class="dropbtn" href="/docs/whodocs.html">Who and Why</a> <div class="dropdown-content"> <a href="/docs/companies.html">Companies</a> <a href="/docs/copyright.html">Copyright</a> <a href="/sponsors.html">Sponsors</a> <a href="/docs/thanks.html">Thanks</a> <a href="/docs/thename.html">The name</a> </div> </div> </div> <div class="contents"> <div class="where"><a href="/">curl</a> / <a href="/docs/">Docs</a> / <a href="/docs/protdocs.html">Protocols</a> / <b>MQTT with curl</b></div>  <h1 id="mqtt-in-curl">MQTT in curl</h1> <h2 id="usage">Usage</h2> <p>A plain "GET" subscribes to the topic and prints all published messages.</p> <p>Doing a "POST" publishes the post data to the topic and exits.</p> <h3 id="subscribing">Subscribing</h3> <p>Command usage:</p> <pre><code>curl mqtt://host/topic</code></pre> <p>Example subscribe:</p> <pre><code>curl mqtt://host.home/bedroom/temp</code></pre> <p>This will send an MQTT SUBSCRIBE packet for the topic <code>bedroom/temp</code> and listen in for incoming PUBLISH packets.</p> <h3 id="publishing">Publishing</h3> <p>Command usage:</p> <pre><code>curl -d payload mqtt://host/topic</code></pre> <p>Example publish:</p> <pre><code>curl -d 75 mqtt://host.home/bedroom/dimmer</code></pre> <p>This will send an MQTT PUBLISH packet to the topic <code>bedroom/dimmer</code> with the payload <code>75</code>.</p> <h2 id="what-does-curl-deliver-as-a-response-to-a-subscribe">What does curl deliver as a response to a subscribe</h2> <p>Whenever a PUBLISH packet is received, curl outputs two bytes topic length (MSB | LSB), the topic followed by the payload.</p> <h2 id="caveats">Caveats</h2> <p>Remaining limitations:</p> <ul> <li>Only QoS level 0 is implemented for publish</li> <li>No way to set retain flag for publish</li> <li>No TLS (mqtts) support</li> <li>Naive EAGAIN handling does not handle split messages</li> </ul> </div> </div> </body> </html>

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MQTT with curl