Added channel example

Examples/Channel.py

@@ -0,0 +1,375 @@
+##########################################################
+# This RNS example demonstrates how to set up a link to  #
+# a destination, and pass structuredmessages over it     #
+# using a channel.                                       #
+##########################################################
+
+import os
+import sys
+import time
+import argparse
+from datetime import datetime
+
+import RNS
+from RNS.vendor import umsgpack
+
+# Let's define an app name. We'll use this for all
+# destinations we create. Since this echo example
+# is part of a range of example utilities, we'll put
+# them all within the app namespace "example_utilities"
+APP_NAME = "example_utilities"
+
+##########################################################
+#### Shared Objects ######################################
+##########################################################
+
+# Channel data must be structured in a subclass of
+# MessageBase. This ensures that the channel will be able
+# to serialize and deserialize the object and multiplex it
+# with other objects. Both ends of a link will need the
+# same object definitions to be able to communicate over
+# a channel.
+#
+# Note: The objects we wish to use over the channel must
+# be registered with the channel, and each link has a
+# different channel instance. See the client_connected
+# and link_established functions in this example to see
+# how message types are registered.
+
+# Let's make a simple message class called StringMessage
+# that will convey a string with a timestamp.
+
+class StringMessage(RNS.MessageBase):
+    # The MSGTYPE class variable needs to be assigned a
+    # 2 byte integer value. This identifier allows the
+    # channel to look up your message's constructor when a
+    # message arrives over the channel.
+    #
+    # MSGTYPE must be unique across all message types we
+    # register with the channel
+    MSGTYPE = 0x0101
+
+    # The constructor of our object must be callable with
+    # no arguments. We can have parameters, but they must
+    # have a default assignment.
+    #
+    # This is needed so the channel can create an empty
+    # version of our message into which the incoming
+    # message can be unpacked.
+    def __init__(self, data=None):
+        self.data = data
+        self.timestamp = datetime.now()
+
+    # Finally, our message needs to implement functions
+    # the channel can call to pack and unpack our message
+    # to/from the raw packet payload. We'll use the
+    # umsgpack package bundled with RNS. We could also use
+    # the struct package bundled with Python if we wanted
+    # more control over the structure of the packed bytes.
+    #
+    # Also note that packed message objects must fit
+    # entirely in one packet. The number of bytes
+    # available for message payloads can be queried from
+    # the channel using the Channel.MDU property. The
+    # channel MDU is slightly less than the link MDU due
+    # to encoding the message header.
+
+    # The pack function encodes the message contents into
+    # a byte stream.
+    def pack(self) -> bytes:
+        return umsgpack.packb((self.data, self.timestamp))
+
+    # And the unpack function decodes a byte stream into
+    # the message contents.
+    def unpack(self, raw):
+        self.data, self.timestamp = umsgpack.unpackb(raw)
+
+
+##########################################################
+#### Server Part #########################################
+##########################################################
+
+# A reference to the latest client link that connected
+latest_client_link = None
+
+# This initialisation is executed when the users chooses
+# to run as a server
+def server(configpath):
+    # We must first initialise Reticulum
+    reticulum = RNS.Reticulum(configpath)
+    
+    # Randomly create a new identity for our link example
+    server_identity = RNS.Identity()
+
+    # We create a destination that clients can connect to. We
+    # want clients to create links to this destination, so we
+    # need to create a "single" destination type.
+    server_destination = RNS.Destination(
+        server_identity,
+        RNS.Destination.IN,
+        RNS.Destination.SINGLE,
+        APP_NAME,
+        "channelexample"
+    )
+
+    # We configure a function that will get called every time
+    # a new client creates a link to this destination.
+    server_destination.set_link_established_callback(client_connected)
+
+    # Everything's ready!
+    # Let's Wait for client requests or user input
+    server_loop(server_destination)
+
+def server_loop(destination):
+    # Let the user know that everything is ready
+    RNS.log(
+        "Link example "+
+        RNS.prettyhexrep(destination.hash)+
+        " running, waiting for a connection."
+    )
+
+    RNS.log("Hit enter to manually send an announce (Ctrl-C to quit)")
+
+    # We enter a loop that runs until the users exits.
+    # If the user hits enter, we will announce our server
+    # destination on the network, which will let clients
+    # know how to create messages directed towards it.
+    while True:
+        entered = input()
+        destination.announce()
+        RNS.log("Sent announce from "+RNS.prettyhexrep(destination.hash))
+
+# When a client establishes a link to our server
+# destination, this function will be called with
+# a reference to the link.
+def client_connected(link):
+    global latest_client_link
+    latest_client_link = link
+
+    RNS.log("Client connected")
+    link.set_link_closed_callback(client_disconnected)
+
+    # Register message types and add callback to channel
+    channel = link.get_channel()
+    channel.register_message_type(StringMessage)
+    channel.add_message_callback(server_message_received)
+
+def client_disconnected(link):
+    RNS.log("Client disconnected")
+
+def server_message_received(message):
+    global latest_client_link
+
+    # When a message is received over any active link,
+    # the replies will all be directed to the last client
+    # that connected.
+    if isinstance(message, StringMessage):
+        RNS.log("Received data on the link: " + message.data + " (message created at " + str(message.timestamp) + ")")
+
+        reply_message = StringMessage("I received \""+message.data+"\" over the link")
+        latest_client_link.get_channel().send(reply_message)
+
+
+##########################################################
+#### Client Part #########################################
+##########################################################
+
+# A reference to the server link
+server_link = None
+
+# This initialisation is executed when the users chooses
+# to run as a client
+def client(destination_hexhash, configpath):
+    # We need a binary representation of the destination
+    # hash that was entered on the command line
+    try:
+        dest_len = (RNS.Reticulum.TRUNCATED_HASHLENGTH//8)*2
+        if len(destination_hexhash) != dest_len:
+            raise ValueError(
+                "Destination length is invalid, must be {hex} hexadecimal characters ({byte} bytes).".format(hex=dest_len, byte=dest_len//2)
+            )
+            
+        destination_hash = bytes.fromhex(destination_hexhash)
+    except:
+        RNS.log("Invalid destination entered. Check your input!\n")
+        exit()
+
+    # We must first initialise Reticulum
+    reticulum = RNS.Reticulum(configpath)
+
+    # Check if we know a path to the destination
+    if not RNS.Transport.has_path(destination_hash):
+        RNS.log("Destination is not yet known. Requesting path and waiting for announce to arrive...")
+        RNS.Transport.request_path(destination_hash)
+        while not RNS.Transport.has_path(destination_hash):
+            time.sleep(0.1)
+
+    # Recall the server identity
+    server_identity = RNS.Identity.recall(destination_hash)
+
+    # Inform the user that we'll begin connecting
+    RNS.log("Establishing link with server...")
+
+    # When the server identity is known, we set
+    # up a destination
+    server_destination = RNS.Destination(
+        server_identity,
+        RNS.Destination.OUT,
+        RNS.Destination.SINGLE,
+        APP_NAME,
+        "channelexample"
+    )
+
+    # And create a link
+    link = RNS.Link(server_destination)
+
+    # We set a callback that will get executed
+    # every time a packet is received over the
+    # link
+    link.set_packet_callback(client_message_received)
+
+    # We'll also set up functions to inform the
+    # user when the link is established or closed
+    link.set_link_established_callback(link_established)
+    link.set_link_closed_callback(link_closed)
+
+    # Everything is set up, so let's enter a loop
+    # for the user to interact with the example
+    client_loop()
+
+def client_loop():
+    global server_link
+
+    # Wait for the link to become active
+    while not server_link:
+        time.sleep(0.1)
+
+    should_quit = False
+    while not should_quit:
+        try:
+            print("> ", end=" ")
+            text = input()
+
+            # Check if we should quit the example
+            if text == "quit" or text == "q" or text == "exit":
+                should_quit = True
+                server_link.teardown()
+
+            # If not, send the entered text over the link
+            if text != "":
+                message = StringMessage(text)
+                packed_size = len(message.pack())
+                channel = server_link.get_channel()
+                if channel.is_ready_to_send():
+                    if packed_size <= channel.MDU:
+                        channel.send(message)
+                    else:
+                        RNS.log(
+                            "Cannot send this packet, the data size of "+
+                            str(packed_size)+" bytes exceeds the link packet MDU of "+
+                            str(channel.MDU)+" bytes",
+                            RNS.LOG_ERROR
+                        )
+                else:
+                    RNS.log("Channel is not ready to send, please wait for " +
+                            "pending messages to complete.", RNS.LOG_ERROR)
+
+        except Exception as e:
+            RNS.log("Error while sending data over the link: "+str(e))
+            should_quit = True
+            server_link.teardown()
+
+# This function is called when a link
+# has been established with the server
+def link_established(link):
+    # We store a reference to the link
+    # instance for later use
+    global server_link
+    server_link = link
+
+    # Register messages and add handler to channel
+    channel = link.get_channel()
+    channel.register_message_type(StringMessage)
+    channel.add_message_callback(client_message_received)
+
+    # Inform the user that the server is
+    # connected
+    RNS.log("Link established with server, enter some text to send, or \"quit\" to quit")
+
+# When a link is closed, we'll inform the
+# user, and exit the program
+def link_closed(link):
+    if link.teardown_reason == RNS.Link.TIMEOUT:
+        RNS.log("The link timed out, exiting now")
+    elif link.teardown_reason == RNS.Link.DESTINATION_CLOSED:
+        RNS.log("The link was closed by the server, exiting now")
+    else:
+        RNS.log("Link closed, exiting now")
+    
+    RNS.Reticulum.exit_handler()
+    time.sleep(1.5)
+    os._exit(0)
+
+# When a packet is received over the link, we
+# simply print out the data.
+def client_message_received(message):
+    if isinstance(message, StringMessage):
+        RNS.log("Received data on the link: " + message.data + " (message created at " + str(message.timestamp) + ")")
+        print("> ", end=" ")
+        sys.stdout.flush()
+
+
+##########################################################
+#### Program Startup #####################################
+##########################################################
+
+# This part of the program runs at startup,
+# and parses input of from the user, and then
+# starts up the desired program mode.
+if __name__ == "__main__":
+    try:
+        parser = argparse.ArgumentParser(description="Simple link example")
+
+        parser.add_argument(
+            "-s",
+            "--server",
+            action="store_true",
+            help="wait for incoming link requests from clients"
+        )
+
+        parser.add_argument(
+            "--config",
+            action="store",
+            default=None,
+            help="path to alternative Reticulum config directory",
+            type=str
+        )
+
+        parser.add_argument(
+            "destination",
+            nargs="?",
+            default=None,
+            help="hexadecimal hash of the server destination",
+            type=str
+        )
+
+        args = parser.parse_args()
+
+        if args.config:
+            configarg = args.config
+        else:
+            configarg = None
+
+        if args.server:
+            server(configarg)
+        else:
+            if (args.destination == None):
+                print("")
+                parser.print_help()
+                print("")
+            else:
+                client(args.destination, configarg)
+
+    except KeyboardInterrupt:
+        print("")
+        exit()