Update README.md

LICENSE.GPLv2

@@ -0,0 +1,340 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
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+in new free programs; and that you know you can do these things.
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+  To protect your rights, we need to make restrictions that forbid
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+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
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+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
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+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
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+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
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+
+Activities other than copying, distribution and modification are not
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+running the Program is not restricted, and the output from the Program
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+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
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+notices that refer to this License and to the absence of any warranty;
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+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
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+  2. You may modify your copy or copies of the Program or any portion
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+
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+
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+These requirements apply to the modified work as a whole.  If
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+distribute the same sections as part of a whole which is a work based
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+
+Thus, it is not the intent of this section to claim rights or contest
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+with the Program (or with a work based on the Program) on a volume of
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+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
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+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
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+prohibited by law if you do not accept this License.  Therefore, by
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+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
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+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
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+through that system in reliance on consistent application of that
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+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
+

README.md

@@ -137,13 +137,13 @@ sudo apt install ntfy
 **Debian/Ubuntu** (*manual install*)**:**
 ```bash
 sudo apt install tmux
-wget https://github.com/binwiederhier/ntfy/releases/download/v1.3.0/ntfy_1.3.0_amd64.deb
-dpkg -i ntfy_1.3.0_amd64.deb
+wget https://github.com/binwiederhier/ntfy/releases/download/v1.4.3/ntfy_1.3.0_amd64.deb
+dpkg -i ntfy_1.4.3_amd64.deb
 ```
 
 **Fedora/RHEL/CentOS:**
 ```bash
-rpm -ivh https://github.com/binwiederhier/ntfy/releases/download/v1.3.0/ntfy_1.3.0_amd64.rpm
+rpm -ivh https://github.com/binwiederhier/ntfy/releases/download/v1.4.3/ntfy_1.3.0_amd64.rpm
 ```
 
 **Docker:**
@@ -158,8 +158,8 @@ go get -u heckel.io/ntfy
 
 **Manual install** (*any x86_64-based Linux*)**:**
 ```bash
-wget https://github.com/binwiederhier/ntfy/releases/download/v1.3.0/ntfy_1.3.0_linux_x86_64.tar.gz
-sudo tar -C /usr/bin -zxf ntfy_1.3.0_linux_x86_64.tar.gz ntfy
+wget https://github.com/binwiederhier/ntfy/releases/download/v1.4.3/ntfy_1.3.0_linux_x86_64.tar.gz
+sudo tar -C /usr/bin -zxf ntfy_1.4.3_linux_x86_64.tar.gz ntfy
 ./ntfy
 ```
 
@@ -176,13 +176,13 @@ To build releases, I use [GoReleaser](https://goreleaser.com/). If you have that
 
 ## TODO
 - add HTTPS
-- make limits configurable
 
 ## Contributing
 I welcome any and all contributions. Just create a PR or an issue.
 
 ## License
-Made with ❤️ by [Philipp C. Heckel](https://heckel.io), distributed under the [Apache License 2.0](LICENSE).
+Made with ❤️ by [Philipp C. Heckel](https://heckel.io).   
+The project is dual licensed under the [Apache License 2.0](LICENSE) and the [GPLv2 License](LICENSE.GPLv2).
 
 Third party libraries and resources:
 * [github.com/urfave/cli/v2](https://github.com/urfave/cli/v2) (MIT) is used to drive the CLI

examples/web-example-eventsource/example-ssh.html

@@ -3,6 +3,7 @@
 <head>
     <meta charset="UTF-8">
     <title>ntfy.sh: EventSource Example</title>
+    <meta name="robots" content="noindex, nofollow" />
     <style>
         body { font-size: 1.2em; line-height: 130%; }
         #events { font-family: monospace; }
@@ -13,6 +14,7 @@
 <p>
     This is an example showing how to use <a href="https://ntfy.sh">ntfy.sh</a> with
     <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventSource">EventSource</a>.<br/>
+    This example doesn't need a server. You can just save the HTML page and run it from anywhere.
 </p>
 <button id="publishButton">Send test notification</button>
 <p><b>Log:</b></p>

server/cache_sqlite.go

@@ -68,6 +68,9 @@ func (c *sqliteCache) Messages(topic string, since sinceTime) ([]*message, error
 		if err := rows.Scan(&id, &timestamp, &msg); err != nil {
 			return nil, err
 		}
+		if msg == "" {
+			msg = " " // Hack: never return empty messages; this should not happen
+		}
 		messages = append(messages, &message{
 			ID:      id,
 			Time:    timestamp,

server/example.html

@@ -0,0 +1,56 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>ntfy.sh: EventSource Example</title>
+    <meta name="robots" content="noindex, nofollow" />
+    <style>
+        body { font-size: 1.2em; line-height: 130%; }
+        #events { font-family: monospace; }
+    </style>
+</head>
+<body>
+<h1>ntfy.sh: EventSource Example</h1>
+<p>
+    This is an example showing how to use <a href="https://ntfy.sh">ntfy.sh</a> with
+    <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventSource">EventSource</a>.<br/>
+    This example doesn't need a server. You can just save the HTML page and run it from anywhere.
+</p>
+<button id="publishButton">Send test notification</button>
+<p><b>Log:</b></p>
+<div id="events"></div>
+
+<script type="text/javascript">
+    const publishURL = `https://ntfy.sh/example`;
+    const subscribeURL = `https://ntfy.sh/example/sse`;
+    const events = document.getElementById('events');
+    const eventSource = new EventSource(subscribeURL);
+
+    // Publish button
+    document.getElementById("publishButton").onclick = () => {
+        fetch(publishURL, {
+            method: 'POST', // works with PUT as well, though that sends an OPTIONS request too!
+            body: `It is ${new Date().toString()}. This is a test.`
+        })
+    };
+
+    // Incoming events
+    eventSource.onopen = () => {
+        let event = document.createElement('div');
+        event.innerHTML = `EventSource connected to ${subscribeURL}`;
+        events.appendChild(event);
+    };
+    eventSource.onerror = (e) => {
+        let event = document.createElement('div');
+        event.innerHTML = `EventSource error: Failed to connect to ${subscribeURL}`;
+        events.appendChild(event);
+    };
+    eventSource.onmessage = (e) => {
+        let event = document.createElement('div');
+        event.innerHTML = e.data;
+        events.appendChild(event);
+    };
+</script>
+
+</body>
+</html>

server/index.gohtml

@@ -13,9 +13,9 @@
     <meta name="HandheldFriendly" content="true">
 
     <!-- Mobile browsers, background color -->
-    <meta name="theme-color" content="#39005a">
-    <meta name="msapplication-navbutton-color" content="#39005a">
-    <meta name="apple-mobile-web-app-status-bar-style" content="#39005a">
+    <meta name="theme-color" content="#317f6f">
+    <meta name="msapplication-navbutton-color" content="#317f6f">
+    <meta name="apple-mobile-web-app-status-bar-style" content="#317f6f">
 
     <!-- Favicon, see favicon.io -->
     <link rel="icon" type="image/png" href="static/img/favicon.png">
@@ -38,7 +38,7 @@
     <h1><img src="static/img/ntfy.png" alt="ntfy"/><br/>ntfy.sh | simple HTTP-based pub-sub</h1>
     <p>
         <b>Ntfy</b> (pronounce: <i>notify</i>) is a simple HTTP-based <a href="https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern">pub-sub</a> notification service.
-        It allows you to send notifications <a href="https://play.google.com/store/apps/details?id=io.heckel.ntfy">to your phone</a> or desktop via scripts from any computer,
+        It allows you to send notifications <a href="#subscribe-phone">to your phone</a> or desktop via scripts from any computer,
         entirely <b>without signup or cost</b>. It's also <a href="https://github.com/binwiederhier/ntfy">open source</a> if you want to run your own.
     </p>
 
@@ -53,21 +53,27 @@
     </div>
 
     <p>
-        There are many ways to use Ntfy. You can send yourself messages for all sorts of things: When a long process finishes or fails (a backup, a long rsync job, ...),
+        There are many ways to use Ntfy. You can send yourself messages for all sorts of things: When a long process finishes or fails,
         or to notify yourself when somebody logs into your server(s). Or you may want to use it in your own app to distribute messages to subscribed clients.
-        Endless possibilities 😀. Be sure to check out the  <a href="https://github.com/binwiederhier/ntfy/tree/main/examples">example on GitHub</a>!
+        Endless possibilities 😀. Be sure to check out the <a href="#examples">examples below</a>.
     </p>
 
-    <h2>Publishing messages</h2>
+    <h2 id="publish" class="anchor">Publishing messages</h2>
     <p>
-        Publishing messages can be done via PUT or POST using. Topics are created on the fly by subscribing or publishing to them.
+        Publishing messages can be done via PUT or POST. Topics are created on the fly by subscribing or publishing to them.
         Because there is no sign-up, <b>the topic is essentially a password</b>, so pick something that's not easily guessable.
     </p>
     <p class="smallMarginBottom">
-        Here's an example showing how to publish a message using <tt>curl</tt>:
+        Here's an example showing how to publish a message using <tt>curl</tt> (via POST):
     </p>
     <code>
-        curl -d "long process is done" ntfy.sh/mytopic
+        curl -d "Backup successful 😀" ntfy.sh/mytopic
+    </code>
+    <p class="smallMarginBottom">
+        And another one using PUT:
+    </p>
+    <code>
+        echo -en "\u26A0\uFE0F Unauthorized login" | curl -sT- ntfy.sh/mytopic
     </code>
     <p class="smallMarginBottom">
         Here's an example in JS with <tt>fetch()</tt> (see <a href="https://github.com/binwiederhier/ntfy/tree/main/examples">full example</a>):
@@ -79,14 +85,14 @@
         })
     </code>
 
-    <h2>Subscribe to a topic</h2>
+    <h2 id="subscribe" class="anchor">Subscribe to a topic</h2>
     <p>
         You can create and subscribe to a topic either in this web UI, or in your own app by subscribing to an
         <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventSource">EventSource</a>, a JSON feed, or raw feed.
     </p>
 
     <div id="subscribeBox">
-        <h3>Subscribe in this Web UI</h3>
+        <h3 id="subscribe-web" class="anchor">Subscribe in this Web UI</h3>
         <p id="error"></p>
         <p>
             Subscribe to topics here and receive messages as <b>desktop notification</b>. Topics are not password-protected,
@@ -104,16 +110,21 @@
         <audio id="notifySound" src="static/sound/mixkit-message-pop-alert-2354.mp3"></audio>
     </div>
 
-    <h3>Subscribe via Android App</h3>
+    <h3 id="subscribe-phone" class="anchor">Subscribe from your phone</h3>
     <p>
         You can use the <a href="https://play.google.com/store/apps/details?id=io.heckel.ntfy">Ntfy Android App</a>
         to receive notifications directly on your phone. Just like the server, this app is also <a href="https://github.com/binwiederhier/ntfy-android">open source</a>.
+        Since I don't have an iPhone or a Mac, I didn't make an iOS app yet. I'd be awesome if <a href="https://github.com/binwiederhier/ntfy/issues/4">someone else could help out</a>.
+    </p>
+    <p>
+        <a href="https://play.google.com/store/apps/details?id=io.heckel.ntfy"><img src="static/img/badge-googleplay.png"></a>
+        <a href="https://github.com/binwiederhier/ntfy/issues/4"><img src="static/img/badge-appstore.png"></a>
     </p>
 
-    <h3>Subscribe via your app, or via the CLI</h3>
+    <h3 id="subscribe-api" class="anchor">Subscribe via your app, or via the CLI</h3>
     <p class="smallMarginBottom">
         Using <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventSource">EventSource</a> in JS, you can consume
-        notifications like this (see <a href="https://github.com/binwiederhier/ntfy/tree/main/examples">full example</a>):
+        notifications like this (see <a href="example.html">live example</a>):
     </p>
     <code>
         const eventSource = new EventSource('https://ntfy.sh/mytopic/sse');<br/>
@@ -149,69 +160,155 @@
     <code>
         $ curl -s ntfy.sh/mytopic/raw<br/>
         <br/>
-        This is a notification
-    </code>
-    <p class="smallMarginBottom">
-        Here's an example of how to use this endpoint to send desktop notifications for every incoming message:
-    </p>
-    <code>
-        while read msg; do<br/>
-        &nbsp;&nbsp;[ -n "$msg" ] && notify-send "$msg"<br/>
-        done < <(stdbuf -i0 -o0 curl -s ntfy.sh/mytopic/raw)
+        This is a notification<br/>
+        And another one with a smiley face 😀
     </code>
 
-    <h3>Message buffering and polling</h3>
+    <h2 id="other-features" class="anchor">Other features</h2>
+    <h3 id="fetching-cached-messages" class="anchor">Fetching cached messages (<tt>since=</tt>)</h3>
     <p class="smallMarginBottom">
-        Messages are buffered in memory for a few hours to account for network interruptions of subscribers.
-        You can read back what you missed by using the <tt>since=...</tt> query parameter. It takes either a
-        duration (e.g. <tt>10m</tt> or <tt>30s</tt>) or a Unix timestamp (e.g. <tt>1635528757</tt>):
+        Messages are cached on disk for {{.CacheDuration}} to account for network interruptions of subscribers.
+        You can read back what you missed by using the <tt>since=</tt> query parameter. It takes either a
+        duration (e.g. <tt>10m</tt> or <tt>30s</tt>), a Unix timestamp (e.g. <tt>1635528757</tt>) or <tt>all</tt> (all
+        cached messages).
     </p>
     <code>
-        $ curl -s "ntfy.sh/mytopic/json?since=10m"<br/>
-        # Same output as above, but includes messages from up to 10 minutes ago
+        curl -s "ntfy.sh/mytopic/json?since=10m"
     </code>
+
+    <h3 id="polling" class="anchor">Polling (<tt>poll=1</tt>)</h3>
     <p class="smallMarginBottom">
         You can also just poll for messages if you don't like the long-standing connection using the <tt>poll=1</tt>
-        query parameter. The connection will end after all available messages have been read. This parameter has to be
-        combined with <tt>since=</tt>.
+        query parameter. The connection will end after all available messages have been read. This parameter can be
+        combined with <tt>since=</tt> (defaults to <tt>since=all</tt>).
     </p>
     <code>
-        $ curl -s "ntfy.sh/mytopic/json?poll=1&since=10m"<br/>
-        # Returns messages from up to 10 minutes ago and ends the connection
+        curl -s "ntfy.sh/mytopic/json?poll=1"
     </code>
 
-    <h2>FAQ</h2>
+    <h3 id="multiple-topics" class="anchor">Subscribing to multiple topics (<tt>topic1,topic2,...</tt>)</h3>
+    <p class="smallMarginBottom">
+        It's possible to subscribe to multiple topics in one HTTP call by providing a
+        comma-separated list of topics in the URL. This allows you to reduce the number of connections you have to maintain:
+    </p>
+    <code>
+        $ curl -s ntfy.sh/mytopic1,mytopic2/json<br/>
+        {"id":"0OkXIryH3H","time":1637182619,"event":"open","topic":"mytopic1,mytopic2,mytopic3"}<br/>
+        {"id":"dzJJm7BCWs","time":1637182634,"event":"message","topic":"mytopic1","message":"for topic 1"}<br/>
+        {"id":"Cm02DsxUHb","time":1637182643,"event":"message","topic":"mytopic2","message":"for topic 2"}
+    </code>
+
+    <h2 id="examples" class="anchor">Examples</h2>
     <p>
-        <b>Isn't this like ...?</b><br/>
+        There are a million ways to use Ntfy, but here are some inspirations. I try to collect
+        <a href="https://github.com/binwiederhier/ntfy/tree/main/examples">examples on GitHub</a>, so be sure to check
+        those out, too.
+    </p>
+
+    <h3 id="example-alerts" class="anchor">Example: A long process is done: backups, copying data, pipelines, ...</h3>
+    <p class="smallMarginBottom">
+        I started adding notifications pretty much all of my scripts. Typically, I just chain the <tt>curl</tt> call
+        directly to the command I'm running. The following example will either send <i>Laptop backup succeeded</i>
+        or ⚠️ <i>Laptop backup failed</i> directly to my phone:
+    </p>
+    <code>
+        rsync -a root@laptop /backups/laptop \<br/>
+        &nbsp;&nbsp;&& zfs snapshot ... \<br/>
+        &nbsp;&nbsp;&& curl -d "Laptop backup succeeded" ntfy.sh/backups \<br/>
+        &nbsp;&nbsp;|| echo -en "\u26A0\uFE0F Laptop backup failed" | curl -sT- ntfy.sh/backups
+    </code>
+
+    <h3 id="example-web" class="anchor">Example: Server-sent messages in your web app</h3>
+    <p>
+        Just as you can <a href="#subscribe-web">subscribe to topics in this Web UI</a>, you can use Ntfy in your own
+        web application. Check out the <a href="example.html">live example</a> or just look the source of this page.
+    </p>
+
+    <h3 id="example-notify-ssh" class="anchor">Example: Notify on SSH login</h3>
+    <p>
+        Years ago my home server was broken into. That shook me hard, so every time someone logs into any machine that I
+        own, I now message myself. Here's an example of how to use <a href="https://en.wikipedia.org/wiki/Linux_PAM">PAM</a>
+        to notify yourself on SSH login.
+    </p>
+    <p class="smallMarginBottom">
+        <b>/etc/pam.d/sshd</b> (at the end of the file):
+    </p>
+    <code>
+        session optional pam_exec.so /usr/local/bin/ntfy-ssh-login.sh
+    </code>
+    <p class="smallMarginBottom">
+        <b>/usr/local/bin/ntfy-ssh-login.sh</b>:
+    </p>
+    <code>
+        #!/bin/bash<br/>
+        if [ "${PAM_TYPE}" = "open_session" ]; then<br/>
+        &nbsp;&nbsp;echo -en "\u26A0\uFE0F SSH login: ${PAM_USER} from ${PAM_RHOST}" | curl -T- ntfy.sh/alerts<br/>
+        fi
+    </code>
+
+    <h3 id="example-collect-data" class="anchor">Example: Collect data from multiple machines</h3>
+    <p>
+        The other day I was running tasks on 20 servers and I wanted to collect the interim results
+        as a CSV in one place. Here's the script I wrote:
+    </p>
+    <code>
+        while read result; do<br/>
+        &nbsp;&nbsp;[ -n "$result" ] && echo "$result" >> results.csv<br/>
+        done < <(stdbuf -i0 -o0 curl -s ntfy.sh/results/raw)
+    </code>
+
+    <h2 id="faq" class="anchor">FAQ</h2>
+    <p>
+        <b id="isnt-this-like" class="anchor">Isn't this like ...?</b><br/>
         Who knows. I didn't do a lot of research before making this. It was fun making it.
     </p>
 
     <p>
-        <b>Can I use this in my app? Will it stay free?</b><br/>
+        <b id="is-it-free" class="anchor">Can I use this in my app? Will it stay free?</b><br/>
         Yes. As long as you don't abuse it, it'll be available and free of charge. I do not plan on monetizing
         the service.
     </p>
 
     <p>
-        <b>What are the uptime guarantees?</b><br/>
+        <b id="uptime-guarantees" class="anchor">What are the uptime guarantees?</b><br/>
         Best effort.
     </p>
 
     <p>
-        <b>Will you know what topics exist, can you spy on me?</b><br/>
-        If you don't trust me or your messages are sensitive, run your own server. It's <a href="https://github.com/binwiederhier/ntfy">open source</a>.
-        That said, the logs do not contain any topic names or other details about you. Check the code if you don't believe me.
+        <b id="multiple-subscribers" class="anchor">What happens if there are multiple subscribers to the same topic?</b><br/>
+        As per usual with pub-sub, all subscribers receive notifications if they are
+        subscribed to a topic.
     </p>
 
     <p>
-        <b>Why is Firebase used?</b><br/>
-        In addition to caching messages locally and delivering them to long-polling subscribers, all messages are also
-        published to Firebase Cloud Messaging (FCM) (if <tt>FirebaseKeyFile</tt> is set, which it is on ntfy.sh). This
-        is to facilitate instant notifications on Android. I tried really, really hard to avoid using FCM, but newer
-        versions of Android made it impossible to implement <a href="https://developer.android.com/guide/background">background services</a>.
+        <b id="can-you-spy-on-me" class="anchor">Will you know what topics exist, can you spy on me?</b><br/>
+        If you don't trust me or your messages are sensitive, run your own server. It's <a href="https://github.com/binwiederhier/ntfy">open source</a>.
+        That said, the logs do not contain any topic names or other details about you.
+        Messages are cached for {{.CacheDuration}} to facilitate service restarts, message polling and to overcome
+        client network disruptions.
     </p>
 
-    <h2>Privacy policy</h2>
+    <p>
+        <b id="selfhosted" class="anchor">Can I self-host it?</b><br/>
+        Yes. The server (including this Web UI) can be self-hosted, and the Android app supports adding topics from
+        your own server as well. There are <a href="https://github.com/binwiederhier/ntfy#installation">install instructions</a>
+        on GitHub.
+    </p>
+
+    <p>
+        <b id="why-firebase" class="anchor">Why is Firebase used?</b><br/>
+        In addition to caching messages locally and delivering them to long-polling subscribers, all messages are also
+        published to Firebase Cloud Messaging (FCM) (if <tt>FirebaseKeyFile</tt> is set, which it is on ntfy.sh). This
+        is to facilitate instant notifications on Android.
+    </p>
+
+    <p>
+        <b id="why-no-ios" class="anchor">Why is there no iOS app (yet)?</b><br/>
+        I don't have an iPhone or a Mac, so I didn't make an iOS app yet. I'd be awesome if
+        <a href="https://github.com/binwiederhier/ntfy/issues/4">someone else could help out</a>.
+    </p>
+
+    <h2 id="privacy" class="anchor">Privacy policy</h2>
     <p>
         Neither the server nor the app record any personal information, or share any of the messages and topics with
         any outside service. All data is exclusively used to make the service function properly. The one exception
@@ -220,7 +317,7 @@
     </p>
     <p>
         The web server does not log or otherwise store request paths, remote IP addresses or even topics or messages,
-        aside from a short on-disk cache (up to a day) to support service restarts.
+        aside from a short on-disk cache (for {{.CacheDuration}}) to support service restarts.
     </p>
 
     <center id="ironicCenterTagDontFreakOut"><i>Made with ❤️ by <a href="https://heckel.io">Philipp C. Heckel</a></i></center>

server/server.go

@@ -78,9 +78,9 @@ const (
 
 var (
 	topicRegex = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}$`) // Regex must match JS & Android app!
-	jsonRegex  = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}/json$`)
-	sseRegex   = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}/sse$`)
-	rawRegex   = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}/raw$`)
+	jsonRegex  = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/json$`)
+	sseRegex   = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/sse$`)
+	rawRegex   = regexp.MustCompile(`^/[-_A-Za-z0-9]{1,64}(,[-_A-Za-z0-9]{1,64})*/raw$`)
 
 	staticRegex = regexp.MustCompile(`^/static/.+`)
 
@@ -88,6 +88,9 @@ var (
 	indexSource   string
 	indexTemplate = template.Must(template.New("index").Parse(indexSource))
 
+	//go:embed "example.html"
+	exampleSource   string
+
 	//go:embed static
 	webStaticFs embed.FS
 
@@ -188,6 +191,8 @@ func (s *Server) handle(w http.ResponseWriter, r *http.Request) {
 func (s *Server) handleInternal(w http.ResponseWriter, r *http.Request) error {
 	if r.Method == http.MethodGet && (r.URL.Path == "/" || topicRegex.MatchString(r.URL.Path)) {
 		return s.handleHome(w, r)
+	} else if r.Method == http.MethodGet && r.URL.Path == "/example.html" {
+		return s.handleExample(w, r)
 	} else if r.Method == http.MethodHead && r.URL.Path == "/" {
 		return s.handleEmpty(w, r)
 	} else if r.Method == http.MethodGet && staticRegex.MatchString(r.URL.Path) {
@@ -217,13 +222,18 @@ func (s *Server) handleEmpty(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
+func (s *Server) handleExample(w http.ResponseWriter, r *http.Request) error {
+	_, err := io.WriteString(w, exampleSource)
+	return err
+}
+
 func (s *Server) handleStatic(w http.ResponseWriter, r *http.Request) error {
 	http.FileServer(http.FS(webStaticFs)).ServeHTTP(w, r)
 	return nil
 }
 
 func (s *Server) handlePublish(w http.ResponseWriter, r *http.Request, v *visitor) error {
-	t, err := s.topic(r.URL.Path[1:])
+	t, err := s.topicFromID(r.URL.Path[1:])
 	if err != nil {
 		return err
 	}
@@ -233,6 +243,9 @@ func (s *Server) handlePublish(w http.ResponseWriter, r *http.Request, v *visito
 		return err
 	}
 	m := newDefaultMessage(t.id, string(b))
+	if m.Message == "" {
+		return errHTTPBadRequest
+	}
 	if err := t.Publish(m); err != nil {
 		return err
 	}
@@ -289,7 +302,9 @@ func (s *Server) handleSubscribe(w http.ResponseWriter, r *http.Request, v *visi
 		return errHTTPTooManyRequests
 	}
 	defer v.RemoveSubscription()
-	t, err := s.topic(strings.TrimSuffix(r.URL.Path[1:], "/"+format)) // Hack
+	topicsStr := strings.TrimSuffix(r.URL.Path[1:], "/"+format) // Hack
+	topicIDs := strings.Split(topicsStr, ",")
+	topics, err := s.topicsFromIDs(topicIDs...)
 	if err != nil {
 		return err
 	}
@@ -314,14 +329,21 @@ func (s *Server) handleSubscribe(w http.ResponseWriter, r *http.Request, v *visi
 	w.Header().Set("Access-Control-Allow-Origin", "*")            // CORS, allow cross-origin requests
 	w.Header().Set("Content-Type", contentType+"; charset=utf-8") // Android/Volley client needs charset!
 	if poll {
-		return s.sendOldMessages(t, since, sub)
+		return s.sendOldMessages(topics, since, sub)
 	}
-	subscriberID := t.Subscribe(sub)
-	defer t.Unsubscribe(subscriberID)
-	if err := sub(newOpenMessage(t.id)); err != nil { // Send out open message
+	subscriberIDs := make([]int, 0)
+	for _, t := range topics {
+		subscriberIDs = append(subscriberIDs, t.Subscribe(sub))
+	}
+	defer func() {
+		for i, subscriberID := range subscriberIDs {
+			topics[i].Unsubscribe(subscriberID) // Order!
+		}
+	}()
+	if err := sub(newOpenMessage(topicsStr)); err != nil { // Send out open message
 		return err
 	}
-	if err := s.sendOldMessages(t, since, sub); err != nil {
+	if err := s.sendOldMessages(topics, since, sub); err != nil {
 		return err
 	}
 	for {
@@ -330,25 +352,27 @@ func (s *Server) handleSubscribe(w http.ResponseWriter, r *http.Request, v *visi
 			return nil
 		case <-time.After(s.config.KeepaliveInterval):
 			v.Keepalive()
-			if err := sub(newKeepaliveMessage(t.id)); err != nil { // Send keepalive message
+			if err := sub(newKeepaliveMessage(topicsStr)); err != nil { // Send keepalive message
 				return err
 			}
 		}
 	}
 }
 
-func (s *Server) sendOldMessages(t *topic, since sinceTime, sub subscriber) error {
+func (s *Server) sendOldMessages(topics []*topic, since sinceTime, sub subscriber) error {
 	if since.IsNone() {
 		return nil
 	}
-	messages, err := s.cache.Messages(t.id, since)
-	if err != nil {
-		return err
-	}
-	for _, m := range messages {
-		if err := sub(m); err != nil {
+	for _, t := range topics {
+		messages, err := s.cache.Messages(t.id, since)
+		if err != nil {
 			return err
 		}
+		for _, m := range messages {
+			if err := sub(m); err != nil {
+				return err
+			}
+		}
 	}
 	return nil
 }
@@ -382,19 +406,31 @@ func (s *Server) handleOptions(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
-func (s *Server) topic(id string) (*topic, error) {
+func (s *Server) topicFromID(id string) (*topic, error) {
+	topics, err := s.topicsFromIDs(id)
+	if err != nil {
+		return nil, err
+	}
+	return topics[0], nil
+}
+
+func (s *Server) topicsFromIDs(ids... string) ([]*topic, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if _, ok := s.topics[id]; !ok {
-		if len(s.topics) >= s.config.GlobalTopicLimit {
-			return nil, errHTTPTooManyRequests
-		}
-		s.topics[id] = newTopic(id, time.Now())
-		if s.firebase != nil {
-			s.topics[id].Subscribe(s.firebase)
+	topics := make([]*topic, 0)
+	for  _, id := range ids {
+		if _, ok := s.topics[id]; !ok {
+			if len(s.topics) >= s.config.GlobalTopicLimit {
+				return nil, errHTTPTooManyRequests
+			}
+			s.topics[id] = newTopic(id, time.Now())
+			if s.firebase != nil {
+				s.topics[id].Subscribe(s.firebase)
+			}
 		}
+		topics = append(topics, s.topics[id])
 	}
-	return s.topics[id], nil
+	return topics, nil
 }
 
 func (s *Server) updateStatsAndExpire() {

server/static/css/app.css

@@ -28,13 +28,13 @@ h1 {
 }
 
 h2 {
-    margin-top: 20px;
+    margin-top: 30px;
     margin-bottom: 5px;
     font-size: 1.8em;
 }
 
 h3 {
-    margin-top: 20px;
+    margin-top: 25px;
     margin-bottom: 5px;
     font-size: 1.3em;
 }
@@ -95,6 +95,24 @@ code {
     color: #666;
 }
 
+/* Anchors */
+
+.anchor .anchorLink {
+    color: #ccc;
+    text-decoration: none;
+    padding: 0 5px;
+    visibility: hidden;
+}
+
+.anchor:hover .anchorLink {
+    visibility: visible;
+}
+
+.anchor .anchorLink:hover {
+    color: #3a9784;
+    visibility: visible;
+}
+
 /* Screenshots */
 
 #screenshots {

server/static/js/app.js

@@ -337,3 +337,13 @@ if (match) {
         currentTopicUnsubscribeOnClose = true;
     }
 }
+
+// Add anchor links
+document.querySelectorAll('.anchor').forEach((el) => {
+    if (el.hasAttribute('id')) {
+        const id = el.getAttribute('id');
+        const anchor = document.createElement('a');
+        anchor.innerHTML = `<a href="#${id}" class="anchorLink">#</a>`;
+        el.appendChild(anchor);
+    }
+});

server/topic.go

@@ -28,6 +28,7 @@ func newTopic(id string, last time.Time) *topic {
 	}
 }
 
+// Subscribe subscribes to this topic
 func (t *topic) Subscribe(s subscriber) int {
 	t.mu.Lock()
 	defer t.mu.Unlock()
@@ -37,24 +38,29 @@ func (t *topic) Subscribe(s subscriber) int {
 	return subscriberID
 }
 
+// Unsubscribe removes the subscription from the list of subscribers
 func (t *topic) Unsubscribe(id int) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	delete(t.subscribers, id)
 }
 
+// Publish asynchronously publishes to all subscribers
 func (t *topic) Publish(m *message) error {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-	t.last = time.Now()
-	for _, s := range t.subscribers {
-		if err := s(m); err != nil {
-			log.Printf("error publishing message to subscriber")
+	go func() {
+		t.mu.Lock()
+		defer t.mu.Unlock()
+		t.last = time.Now()
+		for _, s := range t.subscribers {
+			if err := s(m); err != nil {
+				log.Printf("error publishing message to subscriber")
+			}
 		}
-	}
+	}()
 	return nil
 }
 
+// Subscribers returns the number of subscribers to this topic
 func (t *topic) Subscribers() int {
 	t.mu.Lock()
 	defer t.mu.Unlock()