Updated documentation

docs/manual/_sources/examples.rst.txt

@@ -92,6 +92,18 @@ The *Request* example explores sendig requests and receiving responses.
 
 This example can also be found at `<https://github.com/markqvist/Reticulum/blob/master/Examples/Request.py>`_.
 
+.. _example-channel:
+
+Channel
+=======
+
+The *Channel* example explores using a ``Channel`` to send structured
+data between peers of a ``Link``.
+
+.. literalinclude:: ../../Examples/Channel.py
+
+This example can also be found at `<https://github.com/markqvist/Reticulum/blob/master/Examples/Channel.py>`_.
+
 .. _example-filetransfer:
 
 Filetransfer

docs/manual/_sources/reference.rst.txt

@@ -121,6 +121,34 @@ This chapter lists and explains all classes exposed by the Reticulum Network Sta
 .. autoclass:: RNS.Resource(data, link, advertise=True, auto_compress=True, callback=None, progress_callback=None, timeout=None)
    :members:
 
+.. _api-channel:
+
+.. only:: html
+
+   |start-h3| Channel |end-h3|
+
+.. only:: latex
+
+   Channel
+   -------
+
+.. autoclass:: RNS.Channel.Channel()
+   :members:
+
+.. _api-messsagebase:
+
+.. only:: html
+
+   |start-h3| MessageBase |end-h3|
+
+.. only:: latex
+
+   MessageBase
+   -----------
+
+.. autoclass:: RNS.MessageBase()
+   :members:
+
 .. _api-transport:
 
 .. only:: html

docs/manual/examples.html

@@ -861,6 +861,7 @@ the Packet interface.</p>
             <span class="c1"># If we do not know this destination, tell the</span>
             <span class="c1"># user to wait for an announce to arrive.</span>
             <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Destination is not yet known. Requesting path...&quot;</span><span class="p">)</span>
+            <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Hit enter to manually retry once an announce is received.&quot;</span><span class="p">)</span>
             <span class="n">RNS</span><span class="o">.</span><span class="n">Transport</span><span class="o">.</span><span class="n">request_path</span><span class="p">(</span><span class="n">destination_hash</span><span class="p">)</span>
 
 <span class="c1"># This function is called when our reply destination</span>
@@ -1898,6 +1899,409 @@ the link has been established.</p>
 </div>
 <p>This example can also be found at <a class="reference external" href="https://github.com/markqvist/Reticulum/blob/master/Examples/Request.py">https://github.com/markqvist/Reticulum/blob/master/Examples/Request.py</a>.</p>
 </section>
+<section id="channel">
+<span id="example-channel"></span><h2>Channel<a class="headerlink" href="#channel" title="Permalink to this heading">#</a></h2>
+<p>The <em>Channel</em> example explores using a <code class="docutils literal notranslate"><span class="pre">Channel</span></code> to send structured
+data between peers of a <code class="docutils literal notranslate"><span class="pre">Link</span></code>.</p>
+<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1">##########################################################</span>
+<span class="c1"># This RNS example demonstrates how to set up a link to  #</span>
+<span class="c1"># a destination, and pass structured messages over it    #</span>
+<span class="c1"># using a channel.                                       #</span>
+<span class="c1">##########################################################</span>
+
+<span class="kn">import</span> <span class="nn">os</span>
+<span class="kn">import</span> <span class="nn">sys</span>
+<span class="kn">import</span> <span class="nn">time</span>
+<span class="kn">import</span> <span class="nn">argparse</span>
+<span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">datetime</span>
+
+<span class="kn">import</span> <span class="nn">RNS</span>
+<span class="kn">from</span> <span class="nn">RNS.vendor</span> <span class="kn">import</span> <span class="n">umsgpack</span>
+
+<span class="c1"># Let&#39;s define an app name. We&#39;ll use this for all</span>
+<span class="c1"># destinations we create. Since this echo example</span>
+<span class="c1"># is part of a range of example utilities, we&#39;ll put</span>
+<span class="c1"># them all within the app namespace &quot;example_utilities&quot;</span>
+<span class="n">APP_NAME</span> <span class="o">=</span> <span class="s2">&quot;example_utilities&quot;</span>
+
+<span class="c1">##########################################################</span>
+<span class="c1">#### Shared Objects ######################################</span>
+<span class="c1">##########################################################</span>
+
+<span class="c1"># Channel data must be structured in a subclass of</span>
+<span class="c1"># MessageBase. This ensures that the channel will be able</span>
+<span class="c1"># to serialize and deserialize the object and multiplex it</span>
+<span class="c1"># with other objects. Both ends of a link will need the</span>
+<span class="c1"># same object definitions to be able to communicate over</span>
+<span class="c1"># a channel.</span>
+<span class="c1">#</span>
+<span class="c1"># Note: The objects we wish to use over the channel must</span>
+<span class="c1"># be registered with the channel, and each link has a</span>
+<span class="c1"># different channel instance. See the client_connected</span>
+<span class="c1"># and link_established functions in this example to see</span>
+<span class="c1"># how message types are registered.</span>
+
+<span class="c1"># Let&#39;s make a simple message class called StringMessage</span>
+<span class="c1"># that will convey a string with a timestamp.</span>
+
+<span class="k">class</span> <span class="nc">StringMessage</span><span class="p">(</span><span class="n">RNS</span><span class="o">.</span><span class="n">MessageBase</span><span class="p">):</span>
+    <span class="c1"># The MSGTYPE class variable needs to be assigned a</span>
+    <span class="c1"># 2 byte integer value. This identifier allows the</span>
+    <span class="c1"># channel to look up your message&#39;s constructor when a</span>
+    <span class="c1"># message arrives over the channel.</span>
+    <span class="c1">#</span>
+    <span class="c1"># MSGTYPE must be unique across all message types we</span>
+    <span class="c1"># register with the channel. MSGTYPEs &gt;= 0xf000 are</span>
+    <span class="c1"># reserved for the system.</span>
+    <span class="n">MSGTYPE</span> <span class="o">=</span> <span class="mh">0x0101</span>
+
+    <span class="c1"># The constructor of our object must be callable with</span>
+    <span class="c1"># no arguments. We can have parameters, but they must</span>
+    <span class="c1"># have a default assignment.</span>
+    <span class="c1">#</span>
+    <span class="c1"># This is needed so the channel can create an empty</span>
+    <span class="c1"># version of our message into which the incoming</span>
+    <span class="c1"># message can be unpacked.</span>
+    <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
+        <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="n">data</span>
+        <span class="bp">self</span><span class="o">.</span><span class="n">timestamp</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">()</span>
+
+    <span class="c1"># Finally, our message needs to implement functions</span>
+    <span class="c1"># the channel can call to pack and unpack our message</span>
+    <span class="c1"># to/from the raw packet payload. We&#39;ll use the</span>
+    <span class="c1"># umsgpack package bundled with RNS. We could also use</span>
+    <span class="c1"># the struct package bundled with Python if we wanted</span>
+    <span class="c1"># more control over the structure of the packed bytes.</span>
+    <span class="c1">#</span>
+    <span class="c1"># Also note that packed message objects must fit</span>
+    <span class="c1"># entirely in one packet. The number of bytes</span>
+    <span class="c1"># available for message payloads can be queried from</span>
+    <span class="c1"># the channel using the Channel.MDU property. The</span>
+    <span class="c1"># channel MDU is slightly less than the link MDU due</span>
+    <span class="c1"># to encoding the message header.</span>
+
+    <span class="c1"># The pack function encodes the message contents into</span>
+    <span class="c1"># a byte stream.</span>
+    <span class="k">def</span> <span class="nf">pack</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">bytes</span><span class="p">:</span>
+        <span class="k">return</span> <span class="n">umsgpack</span><span class="o">.</span><span class="n">packb</span><span class="p">((</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">timestamp</span><span class="p">))</span>
+
+    <span class="c1"># And the unpack function decodes a byte stream into</span>
+    <span class="c1"># the message contents.</span>
+    <span class="k">def</span> <span class="nf">unpack</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">raw</span><span class="p">):</span>
+        <span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">timestamp</span> <span class="o">=</span> <span class="n">umsgpack</span><span class="o">.</span><span class="n">unpackb</span><span class="p">(</span><span class="n">raw</span><span class="p">)</span>
+
+
+<span class="c1">##########################################################</span>
+<span class="c1">#### Server Part #########################################</span>
+<span class="c1">##########################################################</span>
+
+<span class="c1"># A reference to the latest client link that connected</span>
+<span class="n">latest_client_link</span> <span class="o">=</span> <span class="kc">None</span>
+
+<span class="c1"># This initialisation is executed when the users chooses</span>
+<span class="c1"># to run as a server</span>
+<span class="k">def</span> <span class="nf">server</span><span class="p">(</span><span class="n">configpath</span><span class="p">):</span>
+    <span class="c1"># We must first initialise Reticulum</span>
+    <span class="n">reticulum</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Reticulum</span><span class="p">(</span><span class="n">configpath</span><span class="p">)</span>
+    
+    <span class="c1"># Randomly create a new identity for our link example</span>
+    <span class="n">server_identity</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Identity</span><span class="p">()</span>
+
+    <span class="c1"># We create a destination that clients can connect to. We</span>
+    <span class="c1"># want clients to create links to this destination, so we</span>
+    <span class="c1"># need to create a &quot;single&quot; destination type.</span>
+    <span class="n">server_destination</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="p">(</span>
+        <span class="n">server_identity</span><span class="p">,</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="o">.</span><span class="n">IN</span><span class="p">,</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="o">.</span><span class="n">SINGLE</span><span class="p">,</span>
+        <span class="n">APP_NAME</span><span class="p">,</span>
+        <span class="s2">&quot;channelexample&quot;</span>
+    <span class="p">)</span>
+
+    <span class="c1"># We configure a function that will get called every time</span>
+    <span class="c1"># a new client creates a link to this destination.</span>
+    <span class="n">server_destination</span><span class="o">.</span><span class="n">set_link_established_callback</span><span class="p">(</span><span class="n">client_connected</span><span class="p">)</span>
+
+    <span class="c1"># Everything&#39;s ready!</span>
+    <span class="c1"># Let&#39;s Wait for client requests or user input</span>
+    <span class="n">server_loop</span><span class="p">(</span><span class="n">server_destination</span><span class="p">)</span>
+
+<span class="k">def</span> <span class="nf">server_loop</span><span class="p">(</span><span class="n">destination</span><span class="p">):</span>
+    <span class="c1"># Let the user know that everything is ready</span>
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span>
+        <span class="s2">&quot;Link example &quot;</span><span class="o">+</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">prettyhexrep</span><span class="p">(</span><span class="n">destination</span><span class="o">.</span><span class="n">hash</span><span class="p">)</span><span class="o">+</span>
+        <span class="s2">&quot; running, waiting for a connection.&quot;</span>
+    <span class="p">)</span>
+
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Hit enter to manually send an announce (Ctrl-C to quit)&quot;</span><span class="p">)</span>
+
+    <span class="c1"># We enter a loop that runs until the users exits.</span>
+    <span class="c1"># If the user hits enter, we will announce our server</span>
+    <span class="c1"># destination on the network, which will let clients</span>
+    <span class="c1"># know how to create messages directed towards it.</span>
+    <span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
+        <span class="n">entered</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span>
+        <span class="n">destination</span><span class="o">.</span><span class="n">announce</span><span class="p">()</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Sent announce from &quot;</span><span class="o">+</span><span class="n">RNS</span><span class="o">.</span><span class="n">prettyhexrep</span><span class="p">(</span><span class="n">destination</span><span class="o">.</span><span class="n">hash</span><span class="p">))</span>
+
+<span class="c1"># When a client establishes a link to our server</span>
+<span class="c1"># destination, this function will be called with</span>
+<span class="c1"># a reference to the link.</span>
+<span class="k">def</span> <span class="nf">client_connected</span><span class="p">(</span><span class="n">link</span><span class="p">):</span>
+    <span class="k">global</span> <span class="n">latest_client_link</span>
+    <span class="n">latest_client_link</span> <span class="o">=</span> <span class="n">link</span>
+
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Client connected&quot;</span><span class="p">)</span>
+    <span class="n">link</span><span class="o">.</span><span class="n">set_link_closed_callback</span><span class="p">(</span><span class="n">client_disconnected</span><span class="p">)</span>
+
+    <span class="c1"># Register message types and add callback to channel</span>
+    <span class="n">channel</span> <span class="o">=</span> <span class="n">link</span><span class="o">.</span><span class="n">get_channel</span><span class="p">()</span>
+    <span class="n">channel</span><span class="o">.</span><span class="n">register_message_type</span><span class="p">(</span><span class="n">StringMessage</span><span class="p">)</span>
+    <span class="n">channel</span><span class="o">.</span><span class="n">add_message_handler</span><span class="p">(</span><span class="n">server_message_received</span><span class="p">)</span>
+
+<span class="k">def</span> <span class="nf">client_disconnected</span><span class="p">(</span><span class="n">link</span><span class="p">):</span>
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Client disconnected&quot;</span><span class="p">)</span>
+
+<span class="k">def</span> <span class="nf">server_message_received</span><span class="p">(</span><span class="n">message</span><span class="p">):</span>
+    <span class="sd">&quot;&quot;&quot;</span>
+<span class="sd">    A message handler</span>
+<span class="sd">    @param message: An instance of a subclass of MessageBase</span>
+<span class="sd">    @return: True if message was handled</span>
+<span class="sd">    &quot;&quot;&quot;</span>
+    <span class="k">global</span> <span class="n">latest_client_link</span>
+    <span class="c1"># When a message is received over any active link,</span>
+    <span class="c1"># the replies will all be directed to the last client</span>
+    <span class="c1"># that connected.</span>
+
+    <span class="c1"># In a message handler, any deserializable message</span>
+    <span class="c1"># that arrives over the link&#39;s channel will be passed</span>
+    <span class="c1"># to all message handlers, unless a preceding handler indicates it</span>
+    <span class="c1"># has handled the message.</span>
+    <span class="c1">#</span>
+    <span class="c1">#</span>
+    <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">StringMessage</span><span class="p">):</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Received data on the link: &quot;</span> <span class="o">+</span> <span class="n">message</span><span class="o">.</span><span class="n">data</span> <span class="o">+</span> <span class="s2">&quot; (message created at &quot;</span> <span class="o">+</span> <span class="nb">str</span><span class="p">(</span><span class="n">message</span><span class="o">.</span><span class="n">timestamp</span><span class="p">)</span> <span class="o">+</span> <span class="s2">&quot;)&quot;</span><span class="p">)</span>
+
+        <span class="n">reply_message</span> <span class="o">=</span> <span class="n">StringMessage</span><span class="p">(</span><span class="s2">&quot;I received </span><span class="se">\&quot;</span><span class="s2">&quot;</span><span class="o">+</span><span class="n">message</span><span class="o">.</span><span class="n">data</span><span class="o">+</span><span class="s2">&quot;</span><span class="se">\&quot;</span><span class="s2"> over the link&quot;</span><span class="p">)</span>
+        <span class="n">latest_client_link</span><span class="o">.</span><span class="n">get_channel</span><span class="p">()</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">reply_message</span><span class="p">)</span>
+
+        <span class="c1"># Incoming messages are sent to each message</span>
+        <span class="c1"># handler added to the channel, in the order they</span>
+        <span class="c1"># were added.</span>
+        <span class="c1"># If any message handler returns True, the message</span>
+        <span class="c1"># is considered handled and any subsequent</span>
+        <span class="c1"># handlers are skipped.</span>
+        <span class="k">return</span> <span class="kc">True</span>
+
+
+<span class="c1">##########################################################</span>
+<span class="c1">#### Client Part #########################################</span>
+<span class="c1">##########################################################</span>
+
+<span class="c1"># A reference to the server link</span>
+<span class="n">server_link</span> <span class="o">=</span> <span class="kc">None</span>
+
+<span class="c1"># This initialisation is executed when the users chooses</span>
+<span class="c1"># to run as a client</span>
+<span class="k">def</span> <span class="nf">client</span><span class="p">(</span><span class="n">destination_hexhash</span><span class="p">,</span> <span class="n">configpath</span><span class="p">):</span>
+    <span class="c1"># We need a binary representation of the destination</span>
+    <span class="c1"># hash that was entered on the command line</span>
+    <span class="k">try</span><span class="p">:</span>
+        <span class="n">dest_len</span> <span class="o">=</span> <span class="p">(</span><span class="n">RNS</span><span class="o">.</span><span class="n">Reticulum</span><span class="o">.</span><span class="n">TRUNCATED_HASHLENGTH</span><span class="o">//</span><span class="mi">8</span><span class="p">)</span><span class="o">*</span><span class="mi">2</span>
+        <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">destination_hexhash</span><span class="p">)</span> <span class="o">!=</span> <span class="n">dest_len</span><span class="p">:</span>
+            <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span>
+                <span class="s2">&quot;Destination length is invalid, must be </span><span class="si">{hex}</span><span class="s2"> hexadecimal characters (</span><span class="si">{byte}</span><span class="s2"> bytes).&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="nb">hex</span><span class="o">=</span><span class="n">dest_len</span><span class="p">,</span> <span class="n">byte</span><span class="o">=</span><span class="n">dest_len</span><span class="o">//</span><span class="mi">2</span><span class="p">)</span>
+            <span class="p">)</span>
+            
+        <span class="n">destination_hash</span> <span class="o">=</span> <span class="nb">bytes</span><span class="o">.</span><span class="n">fromhex</span><span class="p">(</span><span class="n">destination_hexhash</span><span class="p">)</span>
+    <span class="k">except</span><span class="p">:</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Invalid destination entered. Check your input!</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
+        <span class="n">exit</span><span class="p">()</span>
+
+    <span class="c1"># We must first initialise Reticulum</span>
+    <span class="n">reticulum</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Reticulum</span><span class="p">(</span><span class="n">configpath</span><span class="p">)</span>
+
+    <span class="c1"># Check if we know a path to the destination</span>
+    <span class="k">if</span> <span class="ow">not</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Transport</span><span class="o">.</span><span class="n">has_path</span><span class="p">(</span><span class="n">destination_hash</span><span class="p">):</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Destination is not yet known. Requesting path and waiting for announce to arrive...&quot;</span><span class="p">)</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">Transport</span><span class="o">.</span><span class="n">request_path</span><span class="p">(</span><span class="n">destination_hash</span><span class="p">)</span>
+        <span class="k">while</span> <span class="ow">not</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Transport</span><span class="o">.</span><span class="n">has_path</span><span class="p">(</span><span class="n">destination_hash</span><span class="p">):</span>
+            <span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mf">0.1</span><span class="p">)</span>
+
+    <span class="c1"># Recall the server identity</span>
+    <span class="n">server_identity</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Identity</span><span class="o">.</span><span class="n">recall</span><span class="p">(</span><span class="n">destination_hash</span><span class="p">)</span>
+
+    <span class="c1"># Inform the user that we&#39;ll begin connecting</span>
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Establishing link with server...&quot;</span><span class="p">)</span>
+
+    <span class="c1"># When the server identity is known, we set</span>
+    <span class="c1"># up a destination</span>
+    <span class="n">server_destination</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="p">(</span>
+        <span class="n">server_identity</span><span class="p">,</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="o">.</span><span class="n">OUT</span><span class="p">,</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">Destination</span><span class="o">.</span><span class="n">SINGLE</span><span class="p">,</span>
+        <span class="n">APP_NAME</span><span class="p">,</span>
+        <span class="s2">&quot;channelexample&quot;</span>
+    <span class="p">)</span>
+
+    <span class="c1"># And create a link</span>
+    <span class="n">link</span> <span class="o">=</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Link</span><span class="p">(</span><span class="n">server_destination</span><span class="p">)</span>
+
+    <span class="c1"># We set a callback that will get executed</span>
+    <span class="c1"># every time a packet is received over the</span>
+    <span class="c1"># link</span>
+    <span class="n">link</span><span class="o">.</span><span class="n">set_packet_callback</span><span class="p">(</span><span class="n">client_message_received</span><span class="p">)</span>
+
+    <span class="c1"># We&#39;ll also set up functions to inform the</span>
+    <span class="c1"># user when the link is established or closed</span>
+    <span class="n">link</span><span class="o">.</span><span class="n">set_link_established_callback</span><span class="p">(</span><span class="n">link_established</span><span class="p">)</span>
+    <span class="n">link</span><span class="o">.</span><span class="n">set_link_closed_callback</span><span class="p">(</span><span class="n">link_closed</span><span class="p">)</span>
+
+    <span class="c1"># Everything is set up, so let&#39;s enter a loop</span>
+    <span class="c1"># for the user to interact with the example</span>
+    <span class="n">client_loop</span><span class="p">()</span>
+
+<span class="k">def</span> <span class="nf">client_loop</span><span class="p">():</span>
+    <span class="k">global</span> <span class="n">server_link</span>
+
+    <span class="c1"># Wait for the link to become active</span>
+    <span class="k">while</span> <span class="ow">not</span> <span class="n">server_link</span><span class="p">:</span>
+        <span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mf">0.1</span><span class="p">)</span>
+
+    <span class="n">should_quit</span> <span class="o">=</span> <span class="kc">False</span>
+    <span class="k">while</span> <span class="ow">not</span> <span class="n">should_quit</span><span class="p">:</span>
+        <span class="k">try</span><span class="p">:</span>
+            <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;&gt; &quot;</span><span class="p">,</span> <span class="n">end</span><span class="o">=</span><span class="s2">&quot; &quot;</span><span class="p">)</span>
+            <span class="n">text</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span>
+
+            <span class="c1"># Check if we should quit the example</span>
+            <span class="k">if</span> <span class="n">text</span> <span class="o">==</span> <span class="s2">&quot;quit&quot;</span> <span class="ow">or</span> <span class="n">text</span> <span class="o">==</span> <span class="s2">&quot;q&quot;</span> <span class="ow">or</span> <span class="n">text</span> <span class="o">==</span> <span class="s2">&quot;exit&quot;</span><span class="p">:</span>
+                <span class="n">should_quit</span> <span class="o">=</span> <span class="kc">True</span>
+                <span class="n">server_link</span><span class="o">.</span><span class="n">teardown</span><span class="p">()</span>
+
+            <span class="c1"># If not, send the entered text over the link</span>
+            <span class="k">if</span> <span class="n">text</span> <span class="o">!=</span> <span class="s2">&quot;&quot;</span><span class="p">:</span>
+                <span class="n">message</span> <span class="o">=</span> <span class="n">StringMessage</span><span class="p">(</span><span class="n">text</span><span class="p">)</span>
+                <span class="n">packed_size</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">message</span><span class="o">.</span><span class="n">pack</span><span class="p">())</span>
+                <span class="n">channel</span> <span class="o">=</span> <span class="n">server_link</span><span class="o">.</span><span class="n">get_channel</span><span class="p">()</span>
+                <span class="k">if</span> <span class="n">channel</span><span class="o">.</span><span class="n">is_ready_to_send</span><span class="p">():</span>
+                    <span class="k">if</span> <span class="n">packed_size</span> <span class="o">&lt;=</span> <span class="n">channel</span><span class="o">.</span><span class="n">MDU</span><span class="p">:</span>
+                        <span class="n">channel</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">message</span><span class="p">)</span>
+                    <span class="k">else</span><span class="p">:</span>
+                        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span>
+                            <span class="s2">&quot;Cannot send this packet, the data size of &quot;</span><span class="o">+</span>
+                            <span class="nb">str</span><span class="p">(</span><span class="n">packed_size</span><span class="p">)</span><span class="o">+</span><span class="s2">&quot; bytes exceeds the link packet MDU of &quot;</span><span class="o">+</span>
+                            <span class="nb">str</span><span class="p">(</span><span class="n">channel</span><span class="o">.</span><span class="n">MDU</span><span class="p">)</span><span class="o">+</span><span class="s2">&quot; bytes&quot;</span><span class="p">,</span>
+                            <span class="n">RNS</span><span class="o">.</span><span class="n">LOG_ERROR</span>
+                        <span class="p">)</span>
+                <span class="k">else</span><span class="p">:</span>
+                    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Channel is not ready to send, please wait for &quot;</span> <span class="o">+</span>
+                            <span class="s2">&quot;pending messages to complete.&quot;</span><span class="p">,</span> <span class="n">RNS</span><span class="o">.</span><span class="n">LOG_ERROR</span><span class="p">)</span>
+
+        <span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>
+            <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Error while sending data over the link: &quot;</span><span class="o">+</span><span class="nb">str</span><span class="p">(</span><span class="n">e</span><span class="p">))</span>
+            <span class="n">should_quit</span> <span class="o">=</span> <span class="kc">True</span>
+            <span class="n">server_link</span><span class="o">.</span><span class="n">teardown</span><span class="p">()</span>
+
+<span class="c1"># This function is called when a link</span>
+<span class="c1"># has been established with the server</span>
+<span class="k">def</span> <span class="nf">link_established</span><span class="p">(</span><span class="n">link</span><span class="p">):</span>
+    <span class="c1"># We store a reference to the link</span>
+    <span class="c1"># instance for later use</span>
+    <span class="k">global</span> <span class="n">server_link</span>
+    <span class="n">server_link</span> <span class="o">=</span> <span class="n">link</span>
+
+    <span class="c1"># Register messages and add handler to channel</span>
+    <span class="n">channel</span> <span class="o">=</span> <span class="n">link</span><span class="o">.</span><span class="n">get_channel</span><span class="p">()</span>
+    <span class="n">channel</span><span class="o">.</span><span class="n">register_message_type</span><span class="p">(</span><span class="n">StringMessage</span><span class="p">)</span>
+    <span class="n">channel</span><span class="o">.</span><span class="n">add_message_handler</span><span class="p">(</span><span class="n">client_message_received</span><span class="p">)</span>
+
+    <span class="c1"># Inform the user that the server is</span>
+    <span class="c1"># connected</span>
+    <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Link established with server, enter some text to send, or </span><span class="se">\&quot;</span><span class="s2">quit</span><span class="se">\&quot;</span><span class="s2"> to quit&quot;</span><span class="p">)</span>
+
+<span class="c1"># When a link is closed, we&#39;ll inform the</span>
+<span class="c1"># user, and exit the program</span>
+<span class="k">def</span> <span class="nf">link_closed</span><span class="p">(</span><span class="n">link</span><span class="p">):</span>
+    <span class="k">if</span> <span class="n">link</span><span class="o">.</span><span class="n">teardown_reason</span> <span class="o">==</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Link</span><span class="o">.</span><span class="n">TIMEOUT</span><span class="p">:</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;The link timed out, exiting now&quot;</span><span class="p">)</span>
+    <span class="k">elif</span> <span class="n">link</span><span class="o">.</span><span class="n">teardown_reason</span> <span class="o">==</span> <span class="n">RNS</span><span class="o">.</span><span class="n">Link</span><span class="o">.</span><span class="n">DESTINATION_CLOSED</span><span class="p">:</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;The link was closed by the server, exiting now&quot;</span><span class="p">)</span>
+    <span class="k">else</span><span class="p">:</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Link closed, exiting now&quot;</span><span class="p">)</span>
+    
+    <span class="n">RNS</span><span class="o">.</span><span class="n">Reticulum</span><span class="o">.</span><span class="n">exit_handler</span><span class="p">()</span>
+    <span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mf">1.5</span><span class="p">)</span>
+    <span class="n">os</span><span class="o">.</span><span class="n">_exit</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
+
+<span class="c1"># When a packet is received over the link, we</span>
+<span class="c1"># simply print out the data.</span>
+<span class="k">def</span> <span class="nf">client_message_received</span><span class="p">(</span><span class="n">message</span><span class="p">):</span>
+    <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">StringMessage</span><span class="p">):</span>
+        <span class="n">RNS</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="s2">&quot;Received data on the link: &quot;</span> <span class="o">+</span> <span class="n">message</span><span class="o">.</span><span class="n">data</span> <span class="o">+</span> <span class="s2">&quot; (message created at &quot;</span> <span class="o">+</span> <span class="nb">str</span><span class="p">(</span><span class="n">message</span><span class="o">.</span><span class="n">timestamp</span><span class="p">)</span> <span class="o">+</span> <span class="s2">&quot;)&quot;</span><span class="p">)</span>
+        <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;&gt; &quot;</span><span class="p">,</span> <span class="n">end</span><span class="o">=</span><span class="s2">&quot; &quot;</span><span class="p">)</span>
+        <span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
+
+
+<span class="c1">##########################################################</span>
+<span class="c1">#### Program Startup #####################################</span>
+<span class="c1">##########################################################</span>
+
+<span class="c1"># This part of the program runs at startup,</span>
+<span class="c1"># and parses input of from the user, and then</span>
+<span class="c1"># starts up the desired program mode.</span>
+<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>
+    <span class="k">try</span><span class="p">:</span>
+        <span class="n">parser</span> <span class="o">=</span> <span class="n">argparse</span><span class="o">.</span><span class="n">ArgumentParser</span><span class="p">(</span><span class="n">description</span><span class="o">=</span><span class="s2">&quot;Simple link example&quot;</span><span class="p">)</span>
+
+        <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span>
+            <span class="s2">&quot;-s&quot;</span><span class="p">,</span>
+            <span class="s2">&quot;--server&quot;</span><span class="p">,</span>
+            <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span>
+            <span class="n">help</span><span class="o">=</span><span class="s2">&quot;wait for incoming link requests from clients&quot;</span>
+        <span class="p">)</span>
+
+        <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span>
+            <span class="s2">&quot;--config&quot;</span><span class="p">,</span>
+            <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store&quot;</span><span class="p">,</span>
+            <span class="n">default</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span>
+            <span class="n">help</span><span class="o">=</span><span class="s2">&quot;path to alternative Reticulum config directory&quot;</span><span class="p">,</span>
+            <span class="nb">type</span><span class="o">=</span><span class="nb">str</span>
+        <span class="p">)</span>
+
+        <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span>
+            <span class="s2">&quot;destination&quot;</span><span class="p">,</span>
+            <span class="n">nargs</span><span class="o">=</span><span class="s2">&quot;?&quot;</span><span class="p">,</span>
+            <span class="n">default</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span>
+            <span class="n">help</span><span class="o">=</span><span class="s2">&quot;hexadecimal hash of the server destination&quot;</span><span class="p">,</span>
+            <span class="nb">type</span><span class="o">=</span><span class="nb">str</span>
+        <span class="p">)</span>
+
+        <span class="n">args</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>
+
+        <span class="k">if</span> <span class="n">args</span><span class="o">.</span><span class="n">config</span><span class="p">:</span>
+            <span class="n">configarg</span> <span class="o">=</span> <span class="n">args</span><span class="o">.</span><span class="n">config</span>
+        <span class="k">else</span><span class="p">:</span>
+            <span class="n">configarg</span> <span class="o">=</span> <span class="kc">None</span>
+
+        <span class="k">if</span> <span class="n">args</span><span class="o">.</span><span class="n">server</span><span class="p">:</span>
+            <span class="n">server</span><span class="p">(</span><span class="n">configarg</span><span class="p">)</span>
+        <span class="k">else</span><span class="p">:</span>
+            <span class="k">if</span> <span class="p">(</span><span class="n">args</span><span class="o">.</span><span class="n">destination</span> <span class="o">==</span> <span class="kc">None</span><span class="p">):</span>
+                <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;&quot;</span><span class="p">)</span>
+                <span class="n">parser</span><span class="o">.</span><span class="n">print_help</span><span class="p">()</span>
+                <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;&quot;</span><span class="p">)</span>
+            <span class="k">else</span><span class="p">:</span>
+                <span class="n">client</span><span class="p">(</span><span class="n">args</span><span class="o">.</span><span class="n">destination</span><span class="p">,</span> <span class="n">configarg</span><span class="p">)</span>
+
+    <span class="k">except</span> <span class="ne">KeyboardInterrupt</span><span class="p">:</span>
+        <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;&quot;</span><span class="p">)</span>
+        <span class="n">exit</span><span class="p">()</span>
+</pre></div>
+</div>
+<p>This example can also be found at <a class="reference external" href="https://github.com/markqvist/Reticulum/blob/master/Examples/Channel.py">https://github.com/markqvist/Reticulum/blob/master/Examples/Channel.py</a>.</p>
+</section>
 <section id="filetransfer">
 <span id="example-filetransfer"></span><h2>Filetransfer<a class="headerlink" href="#filetransfer" title="Permalink to this heading">#</a></h2>
 <p>The <em>Filetransfer</em> example implements a basic file-server program that
@@ -2578,6 +2982,7 @@ interface to efficiently pass files of any size over a Reticulum <a class="refer
 <li><a class="reference internal" href="#link">Link</a></li>
 <li><a class="reference internal" href="#example-identify">Identification</a></li>
 <li><a class="reference internal" href="#requests-responses">Requests &amp; Responses</a></li>
+<li><a class="reference internal" href="#channel">Channel</a></li>
 <li><a class="reference internal" href="#filetransfer">Filetransfer</a></li>
 </ul>
 </li>

docs/manual/genindex.html

@@ -222,13 +222,15 @@
           
 <section class="genindex-section">
   <h1 id="index">Index</h1>
-  <div class="genindex-jumpbox"><a href="#A"><strong>A</strong></a> | <a href="#C"><strong>C</strong></a> | <a href="#D"><strong>D</strong></a> | <a href="#E"><strong>E</strong></a> | <a href="#F"><strong>F</strong></a> | <a href="#G"><strong>G</strong></a> | <a href="#H"><strong>H</strong></a> | <a href="#I"><strong>I</strong></a> | <a href="#K"><strong>K</strong></a> | <a href="#L"><strong>L</strong></a> | <a href="#M"><strong>M</strong></a> | <a href="#N"><strong>N</strong></a> | <a href="#P"><strong>P</strong></a> | <a href="#R"><strong>R</strong></a> | <a href="#S"><strong>S</strong></a> | <a href="#T"><strong>T</strong></a> | <a href="#V"><strong>V</strong></a></div>
+  <div class="genindex-jumpbox"><a href="#A"><strong>A</strong></a> | <a href="#C"><strong>C</strong></a> | <a href="#D"><strong>D</strong></a> | <a href="#E"><strong>E</strong></a> | <a href="#F"><strong>F</strong></a> | <a href="#G"><strong>G</strong></a> | <a href="#H"><strong>H</strong></a> | <a href="#I"><strong>I</strong></a> | <a href="#K"><strong>K</strong></a> | <a href="#L"><strong>L</strong></a> | <a href="#M"><strong>M</strong></a> | <a href="#N"><strong>N</strong></a> | <a href="#P"><strong>P</strong></a> | <a href="#R"><strong>R</strong></a> | <a href="#S"><strong>S</strong></a> | <a href="#T"><strong>T</strong></a> | <a href="#U"><strong>U</strong></a> | <a href="#V"><strong>V</strong></a></div>
 </section>
 <section id="A" class="genindex-section">
   <h2>A</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
         <li><a href="reference.html#RNS.Destination.accepts_links">accepts_links() (RNS.Destination method)</a>
+</li>
+        <li><a href="reference.html#RNS.Channel.Channel.add_message_handler">add_message_handler() (RNS.Channel.Channel method)</a>
 </li>
         <li><a href="reference.html#RNS.Resource.advertise">advertise() (RNS.Resource method)</a>
 </li>
@@ -249,6 +251,8 @@
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
         <li><a href="reference.html#RNS.Resource.cancel">cancel() (RNS.Resource method)</a>
+</li>
+        <li><a href="reference.html#RNS.Channel.Channel">Channel (class in RNS.Channel)</a>
 </li>
         <li><a href="reference.html#RNS.Destination.clear_default_app_data">clear_default_app_data() (RNS.Destination method)</a>
 </li>
@@ -330,6 +334,8 @@
   <h2>G</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.Link.get_channel">get_channel() (RNS.Link method)</a>
+</li>
         <li><a href="reference.html#RNS.Resource.get_data_size">get_data_size() (RNS.Resource method)</a>
 </li>
         <li><a href="reference.html#RNS.Link.get_establishment_rate">get_establishment_rate() (RNS.Link method)</a>
@@ -411,6 +417,8 @@
         <li><a href="reference.html#RNS.Link.inactive_for">inactive_for() (RNS.Link method)</a>
 </li>
         <li><a href="reference.html#RNS.Resource.is_compressed">is_compressed() (RNS.Resource method)</a>
+</li>
+        <li><a href="reference.html#RNS.Channel.Channel.is_ready_to_send">is_ready_to_send() (RNS.Channel.Channel method)</a>
 </li>
     </ul></td>
   </tr></table>
@@ -456,6 +464,14 @@
   <h2>M</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.Channel.Channel.MDU">MDU (RNS.Channel.Channel property)</a>
+</li>
+        <li><a href="reference.html#RNS.MessageBase">MessageBase (class in RNS)</a>
+</li>
+    </ul></td>
+    <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.MessageBase.MSGTYPE">MSGTYPE (RNS.MessageBase attribute)</a>
+</li>
         <li><a href="reference.html#RNS.Reticulum.MTU">MTU (RNS.Reticulum attribute)</a>
 </li>
     </ul></td>
@@ -484,12 +500,14 @@
   <h2>P</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
-        <li><a href="reference.html#RNS.Packet">Packet (class in RNS)</a>
+        <li><a href="reference.html#RNS.MessageBase.pack">pack() (RNS.MessageBase method)</a>
 </li>
-        <li><a href="reference.html#RNS.PacketReceipt">PacketReceipt (class in RNS)</a>
+        <li><a href="reference.html#RNS.Packet">Packet (class in RNS)</a>
 </li>
     </ul></td>
     <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.PacketReceipt">PacketReceipt (class in RNS)</a>
+</li>
         <li><a href="reference.html#RNS.Transport.PATHFINDER_M">PATHFINDER_M (RNS.Transport attribute)</a>
 </li>
         <li><a href="reference.html#RNS.Packet.PLAIN_MDU">PLAIN_MDU (RNS.Packet attribute)</a>
@@ -507,13 +525,17 @@
         <li><a href="reference.html#RNS.Identity.recall_app_data">recall_app_data() (RNS.Identity static method)</a>
 </li>
         <li><a href="reference.html#RNS.Transport.register_announce_handler">register_announce_handler() (RNS.Transport static method)</a>
+</li>
+        <li><a href="reference.html#RNS.Channel.Channel.register_message_type">register_message_type() (RNS.Channel.Channel method)</a>
 </li>
         <li><a href="reference.html#RNS.Destination.register_request_handler">register_request_handler() (RNS.Destination method)</a>
 </li>
-        <li><a href="reference.html#RNS.Link.request">request() (RNS.Link method)</a>
+        <li><a href="reference.html#RNS.Channel.Channel.remove_message_handler">remove_message_handler() (RNS.Channel.Channel method)</a>
 </li>
     </ul></td>
     <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.Link.request">request() (RNS.Link method)</a>
+</li>
         <li><a href="reference.html#RNS.Transport.request_path">request_path() (RNS.Transport static method)</a>
 </li>
         <li><a href="reference.html#RNS.RequestReceipt">RequestReceipt (class in RNS)</a>
@@ -532,8 +554,12 @@
   <h2>S</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>
     <td style="width: 33%; vertical-align: top;"><ul>
-        <li><a href="reference.html#RNS.Packet.send">send() (RNS.Packet method)</a>
+        <li><a href="reference.html#RNS.Channel.Channel.send">send() (RNS.Channel.Channel method)</a>
+
+        <ul>
+          <li><a href="reference.html#RNS.Packet.send">(RNS.Packet method)</a>
 </li>
+        </ul></li>
         <li><a href="reference.html#RNS.Destination.set_default_app_data">set_default_app_data() (RNS.Destination method)</a>
 </li>
         <li><a href="reference.html#RNS.PacketReceipt.set_delivery_callback">set_delivery_callback() (RNS.PacketReceipt method)</a>
@@ -606,6 +632,16 @@
   </tr></table>
 </section>
 
+<section id="U" class="genindex-section">
+  <h2>U</h2>
+  <table style="width: 100%" class="indextable genindextable"><tr>
+    <td style="width: 33%; vertical-align: top;"><ul>
+        <li><a href="reference.html#RNS.MessageBase.unpack">unpack() (RNS.MessageBase method)</a>
+</li>
+    </ul></td>
+  </tr></table>
+</section>
+
 <section id="V" class="genindex-section">
   <h2>V</h2>
   <table style="width: 100%" class="indextable genindextable"><tr>

docs/manual/index.html

@@ -355,6 +355,7 @@ to participate in the development of Reticulum itself.</p>
 <li class="toctree-l2"><a class="reference internal" href="examples.html#link">Link</a></li>
 <li class="toctree-l2"><a class="reference internal" href="examples.html#example-identify">Identification</a></li>
 <li class="toctree-l2"><a class="reference internal" href="examples.html#requests-responses">Requests &amp; Responses</a></li>
+<li class="toctree-l2"><a class="reference internal" href="examples.html#channel">Channel</a></li>
 <li class="toctree-l2"><a class="reference internal" href="examples.html#filetransfer">Filetransfer</a></li>
 </ul>
 </li>
@@ -377,6 +378,8 @@ to participate in the development of Reticulum itself.</p>
 <li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.Link"><code class="docutils literal notranslate"><span class="pre">Link</span></code></a></li>
 <li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.RequestReceipt"><code class="docutils literal notranslate"><span class="pre">RequestReceipt</span></code></a></li>
 <li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.Resource"><code class="docutils literal notranslate"><span class="pre">Resource</span></code></a></li>
+<li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.Channel.Channel"><code class="docutils literal notranslate"><span class="pre">Channel</span></code></a></li>
+<li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.MessageBase"><code class="docutils literal notranslate"><span class="pre">MessageBase</span></code></a></li>
 <li class="toctree-l2"><a class="reference internal" href="reference.html#RNS.Transport"><code class="docutils literal notranslate"><span class="pre">Transport</span></code></a></li>
 </ul>
 </li>

docs/manual/reference.html

@@ -1114,6 +1114,17 @@ thus preserved. This method can be used for authentication.</p>
 be used if a new link to the same destination is established.</p>
 </dd></dl>
 
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Link.get_channel">
+<span class="sig-name descname"><span class="pre">get_channel</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#RNS.Link.get_channel" title="Permalink to this definition">#</a></dt>
+<dd><p>Get the <code class="docutils literal notranslate"><span class="pre">Channel</span></code> for this link.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Returns</dt>
+<dd class="field-odd"><p><code class="docutils literal notranslate"><span class="pre">Channel</span></code> object</p>
+</dd>
+</dl>
+</dd></dl>
+
 <dl class="py method">
 <dt class="sig sig-object py" id="RNS.Link.set_link_closed_callback">
 <span class="sig-name descname"><span class="pre">set_link_closed_callback</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#RNS.Link.set_link_closed_callback" title="Permalink to this definition">#</a></dt>
@@ -1367,6 +1378,153 @@ the resource advertisement it will begin transferring.</p>
 
 </dd></dl>
 
+<p id="api-channel"><h3> Channel </h3></p>
+<dl class="py class">
+<dt class="sig sig-object py" id="RNS.Channel.Channel">
+<em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">RNS.Channel.</span></span><span class="sig-name descname"><span class="pre">Channel</span></span><a class="headerlink" href="#RNS.Channel.Channel" title="Permalink to this definition">#</a></dt>
+<dd><p>Provides reliable delivery of messages over
+a link.</p>
+<p><code class="docutils literal notranslate"><span class="pre">Channel</span></code> differs from <code class="docutils literal notranslate"><span class="pre">Request</span></code> and
+<code class="docutils literal notranslate"><span class="pre">Resource</span></code> in some important ways:</p>
+<blockquote>
+<div><dl class="simple">
+<dt><strong>Continuous</strong></dt><dd><p>Messages can be sent or received as long as
+the <code class="docutils literal notranslate"><span class="pre">Link</span></code> is open.</p>
+</dd>
+<dt><strong>Bi-directional</strong></dt><dd><p>Messages can be sent in either direction on
+the <code class="docutils literal notranslate"><span class="pre">Link</span></code>; neither end is the client or
+server.</p>
+</dd>
+<dt><strong>Size-constrained</strong></dt><dd><p>Messages must be encoded into a single packet.</p>
+</dd>
+</dl>
+</div></blockquote>
+<p><code class="docutils literal notranslate"><span class="pre">Channel</span></code> is similar to <code class="docutils literal notranslate"><span class="pre">Packet</span></code>, except that it
+provides reliable delivery (automatic retries) as well
+as a structure for exchanging several types of
+messages over the <code class="docutils literal notranslate"><span class="pre">Link</span></code>.</p>
+<p><code class="docutils literal notranslate"><span class="pre">Channel</span></code> is not instantiated directly, but rather
+obtained from a <code class="docutils literal notranslate"><span class="pre">Link</span></code> with <code class="docutils literal notranslate"><span class="pre">get_channel()</span></code>.</p>
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.register_message_type">
+<span class="sig-name descname"><span class="pre">register_message_type</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">message_class</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">Type</span><span class="p"><span class="pre">[</span></span><a class="reference internal" href="#RNS.MessageBase" title="RNS.Channel.MessageBase"><span class="pre">MessageBase</span></a><span class="p"><span class="pre">]</span></span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#RNS.Channel.Channel.register_message_type" title="Permalink to this definition">#</a></dt>
+<dd><p>Register a message class for reception over a <code class="docutils literal notranslate"><span class="pre">Channel</span></code>.</p>
+<p>Message classes must extend <code class="docutils literal notranslate"><span class="pre">MessageBase</span></code>.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Parameters</dt>
+<dd class="field-odd"><p><strong>message_class</strong> – Class to register</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.add_message_handler">
+<span class="sig-name descname"><span class="pre">add_message_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">MessageCallbackType</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#RNS.Channel.Channel.add_message_handler" title="Permalink to this definition">#</a></dt>
+<dd><p>Add a handler for incoming messages. A handler
+has the following signature:</p>
+<p><code class="docutils literal notranslate"><span class="pre">(message:</span> <span class="pre">MessageBase)</span> <span class="pre">-&gt;</span> <span class="pre">bool</span></code></p>
+<p>Handlers are processed in the order they are
+added. If any handler returns True, processing
+of the message stops; handlers after the
+returning handler will not be called.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Parameters</dt>
+<dd class="field-odd"><p><strong>callback</strong> – Function to call</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.remove_message_handler">
+<span class="sig-name descname"><span class="pre">remove_message_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">MessageCallbackType</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#RNS.Channel.Channel.remove_message_handler" title="Permalink to this definition">#</a></dt>
+<dd><p>Remove a handler added with <code class="docutils literal notranslate"><span class="pre">add_message_handler</span></code>.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Parameters</dt>
+<dd class="field-odd"><p><strong>callback</strong> – handler to remove</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.is_ready_to_send">
+<span class="sig-name descname"><span class="pre">is_ready_to_send</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">&#x2192;</span> <span class="sig-return-typehint"><span class="pre">bool</span></span></span><a class="headerlink" href="#RNS.Channel.Channel.is_ready_to_send" title="Permalink to this definition">#</a></dt>
+<dd><p>Check if <code class="docutils literal notranslate"><span class="pre">Channel</span></code> is ready to send.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Returns</dt>
+<dd class="field-odd"><p>True if ready</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.send">
+<span class="sig-name descname"><span class="pre">send</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">message</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><a class="reference internal" href="#RNS.MessageBase" title="RNS.Channel.MessageBase"><span class="pre">MessageBase</span></a></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">&#x2192;</span> <span class="sig-return-typehint"><span class="pre">Envelope</span></span></span><a class="headerlink" href="#RNS.Channel.Channel.send" title="Permalink to this definition">#</a></dt>
+<dd><p>Send a message. If a message send is attempted and
+<code class="docutils literal notranslate"><span class="pre">Channel</span></code> is not ready, an exception is thrown.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Parameters</dt>
+<dd class="field-odd"><p><strong>message</strong> – an instance of a <code class="docutils literal notranslate"><span class="pre">MessageBase</span></code> subclass</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py property">
+<dt class="sig sig-object py" id="RNS.Channel.Channel.MDU">
+<em class="property"><span class="pre">property</span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">MDU</span></span><a class="headerlink" href="#RNS.Channel.Channel.MDU" title="Permalink to this definition">#</a></dt>
+<dd><p>Maximum Data Unit: the number of bytes available
+for a message to consume in a single send. This
+value is adjusted from the <code class="docutils literal notranslate"><span class="pre">Link</span></code> MDU to accommodate
+message header information.</p>
+<dl class="field-list simple">
+<dt class="field-odd">Returns</dt>
+<dd class="field-odd"><p>number of bytes available</p>
+</dd>
+</dl>
+</dd></dl>
+
+</dd></dl>
+
+<p id="api-messsagebase"><h3> MessageBase </h3></p>
+<dl class="py class">
+<dt class="sig sig-object py" id="RNS.MessageBase">
+<em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">RNS.</span></span><span class="sig-name descname"><span class="pre">MessageBase</span></span><a class="headerlink" href="#RNS.MessageBase" title="Permalink to this definition">#</a></dt>
+<dd><p>Base type for any messages sent or received on a Channel.
+Subclasses must define the two abstract methods as well as
+the <code class="docutils literal notranslate"><span class="pre">MSGTYPE</span></code> class variable.</p>
+<dl class="py attribute">
+<dt class="sig sig-object py" id="RNS.MessageBase.MSGTYPE">
+<span class="sig-name descname"><span class="pre">MSGTYPE</span></span><em class="property"><span class="w"> </span><span class="p"><span class="pre">=</span></span><span class="w"> </span><span class="pre">None</span></em><a class="headerlink" href="#RNS.MessageBase.MSGTYPE" title="Permalink to this definition">#</a></dt>
+<dd><p>Defines a unique identifier for a message class.</p>
+<ul class="simple">
+<li><p>Must be unique within all classes registered with a <code class="docutils literal notranslate"><span class="pre">Channel</span></code></p></li>
+<li><p>Must be less than <code class="docutils literal notranslate"><span class="pre">0xf000</span></code>. Values greater than or equal to <code class="docutils literal notranslate"><span class="pre">0xf000</span></code> are reserved.</p></li>
+</ul>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.MessageBase.pack">
+<em class="property"><span class="pre">abstract</span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">pack</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">&#x2192;</span> <span class="sig-return-typehint"><span class="pre">bytes</span></span></span><a class="headerlink" href="#RNS.MessageBase.pack" title="Permalink to this definition">#</a></dt>
+<dd><p>Create and return the binary representation of the message</p>
+<dl class="field-list simple">
+<dt class="field-odd">Returns</dt>
+<dd class="field-odd"><p>binary representation of message</p>
+</dd>
+</dl>
+</dd></dl>
+
+<dl class="py method">
+<dt class="sig sig-object py" id="RNS.MessageBase.unpack">
+<em class="property"><span class="pre">abstract</span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">unpack</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">raw</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">bytes</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#RNS.MessageBase.unpack" title="Permalink to this definition">#</a></dt>
+<dd><p>Populate message from binary representation</p>
+<dl class="field-list simple">
+<dt class="field-odd">Parameters</dt>
+<dd class="field-odd"><p><strong>raw</strong> – binary representation</p>
+</dd>
+</dl>
+</dd></dl>
+
+</dd></dl>
+
 <p id="api-transport"><h3> Transport </h3></p>
 <dl class="py class">
 <dt class="sig sig-object py" id="RNS.Transport">
@@ -1604,6 +1762,7 @@ will announce it.</p>
 <li><a class="reference internal" href="#RNS.Link.inactive_for"><code class="docutils literal notranslate"><span class="pre">inactive_for()</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Link.get_remote_identity"><code class="docutils literal notranslate"><span class="pre">get_remote_identity()</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Link.teardown"><code class="docutils literal notranslate"><span class="pre">teardown()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Link.get_channel"><code class="docutils literal notranslate"><span class="pre">get_channel()</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Link.set_link_closed_callback"><code class="docutils literal notranslate"><span class="pre">set_link_closed_callback()</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Link.set_packet_callback"><code class="docutils literal notranslate"><span class="pre">set_packet_callback()</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Link.set_resource_callback"><code class="docutils literal notranslate"><span class="pre">set_resource_callback()</span></code></a></li>
@@ -1633,6 +1792,21 @@ will announce it.</p>
 <li><a class="reference internal" href="#RNS.Resource.is_compressed"><code class="docutils literal notranslate"><span class="pre">is_compressed()</span></code></a></li>
 </ul>
 </li>
+<li><a class="reference internal" href="#RNS.Channel.Channel"><code class="docutils literal notranslate"><span class="pre">Channel</span></code></a><ul>
+<li><a class="reference internal" href="#RNS.Channel.Channel.register_message_type"><code class="docutils literal notranslate"><span class="pre">register_message_type()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Channel.Channel.add_message_handler"><code class="docutils literal notranslate"><span class="pre">add_message_handler()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Channel.Channel.remove_message_handler"><code class="docutils literal notranslate"><span class="pre">remove_message_handler()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Channel.Channel.is_ready_to_send"><code class="docutils literal notranslate"><span class="pre">is_ready_to_send()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Channel.Channel.send"><code class="docutils literal notranslate"><span class="pre">send()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.Channel.Channel.MDU"><code class="docutils literal notranslate"><span class="pre">MDU</span></code></a></li>
+</ul>
+</li>
+<li><a class="reference internal" href="#RNS.MessageBase"><code class="docutils literal notranslate"><span class="pre">MessageBase</span></code></a><ul>
+<li><a class="reference internal" href="#RNS.MessageBase.MSGTYPE"><code class="docutils literal notranslate"><span class="pre">MSGTYPE</span></code></a></li>
+<li><a class="reference internal" href="#RNS.MessageBase.pack"><code class="docutils literal notranslate"><span class="pre">pack()</span></code></a></li>
+<li><a class="reference internal" href="#RNS.MessageBase.unpack"><code class="docutils literal notranslate"><span class="pre">unpack()</span></code></a></li>
+</ul>
+</li>
 <li><a class="reference internal" href="#RNS.Transport"><code class="docutils literal notranslate"><span class="pre">Transport</span></code></a><ul>
 <li><a class="reference internal" href="#RNS.Transport.PATHFINDER_M"><code class="docutils literal notranslate"><span class="pre">PATHFINDER_M</span></code></a></li>
 <li><a class="reference internal" href="#RNS.Transport.register_announce_handler"><code class="docutils literal notranslate"><span class="pre">register_announce_handler()</span></code></a></li>

docs/source/examples.rst

@@ -95,7 +95,7 @@ This example can also be found at `<https://github.com/markqvist/Reticulum/blob/
 .. _example-channel:
 
 Channel
-====
+=======
 
 The *Channel* example explores using a ``Channel`` to send structured
 data between peers of a ``Link``.

docs/source/reference.rst

@@ -130,7 +130,7 @@ This chapter lists and explains all classes exposed by the Reticulum Network Sta
 .. only:: latex
 
    Channel
-   ------
+   -------
 
 .. autoclass:: RNS.Channel.Channel()
    :members:
@@ -144,7 +144,7 @@ This chapter lists and explains all classes exposed by the Reticulum Network Sta
 .. only:: latex
 
    MessageBase
-   ------
+   -----------
 
 .. autoclass:: RNS.MessageBase()
    :members: