RosSubscriber.py

##########################################################
# This RNS example demonstrates how to set perform       #
# requests and receive responses over a link.            #
##########################################################
import os
import sys
import time
import random
import argparse
import RNS

import rospy
from std_msgs.msg import String


# 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 "RosSubscriber"
APP_NAME = "RosSubscriber"

# define a fixed key for hashing RNS identity
key_hash = ("8893e2bfd30fc08455997caf7abb7a6341716768dbbf9a91cc1455bd7eeaf74cdc10ec72a4d4179696040bac620ee97ebc861e2443e5270537ae766d91b58181", "4461a04223203527d1053d1daed5e853")

##########################################################
#### Server Part #########################################
##########################################################

# A reference to the latest client link that connected
latest_client_link = None

# Buffer of ros message
ros_msg = ""

def ros_subsciber_callback(path, data, request_id, link_id, remote_identity, requested_at):
    global ros_msg
    RNS.log("Generating response to request "+RNS.prettyhexrep(request_id)+" on link "+RNS.prettyhexrep(link_id))
    return "/reticulum/in topic:\n" + ros_msg + "\n"

def callback(msg):
    global ros_msg
    # RNS.log("Recieved new ROS message: \n", msg.data)
    ros_msg = msg.data
    # rospy.loginfo(rospy.get_caller_id() + "I heard %s", data.data)

# 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()

    # generate identity hash from specified key
    key, id_hash = key_hash
    server_identity = RNS.Identity.from_bytes(bytes.fromhex(key))

    # 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,
        "requestexample"
    )

    # 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)

    # We register a request handler for handling incoming
    # requests over any established links.
    server_destination.register_request_handler(
        "/reticulum/in",
        response_generator = ros_subsciber_callback,
        allow = RNS.Destination.ALLOW_ALL
    )

    # Initialize Ros listener node 
    rospy.init_node('listener_node', anonymous=True)

    # 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(
        "Request 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

    RNS.log("Client connected")
    link.set_link_closed_callback(client_disconnected)
    latest_client_link = link

    # subscribe to the topic, specifing the data (String) and a callback function to handle new topic message
    rospy.Subscriber("/reticulum/in", String, callback)

def client_disconnected(link):
    RNS.log("Client disconnected")


##########################################################
#### 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,
        "requestexample"
    )

    # And create a link
    link = RNS.Link(server_destination)

    # We'll 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()

            else:
                server_link.request(
                    "/reticulum/in",
                    data = None,
                    response_callback = got_response,
                    failed_callback = request_failed
                )


        except Exception as e:
            RNS.log("Error while sending request over the link: "+str(e))
            should_quit = True
            server_link.teardown()

def got_response(request_receipt):
    request_id = request_receipt.request_id
    response = request_receipt.response

    RNS.log("Got response for request "+RNS.prettyhexrep(request_id)+": "+str(response))

def request_received(request_receipt):
    RNS.log("The request "+RNS.prettyhexrep(request_receipt.request_id)+" was received by the remote peer.")

def request_failed(request_receipt):
    RNS.log("The request "+RNS.prettyhexrep(request_receipt.request_id)+" failed.")


# 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

    # Inform the user that the server is
    # connected
    RNS.log("Link established with server, hit enter to perform a request, or type in \"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)


##########################################################
#### 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 request/response example")

        parser.add_argument(
            "-s",
            "--server",
            action="store_true",
            help="wait for incoming 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()