Engineering Clinic

ROS1 Noetic -Publisher and Subscriber Example This post tells about the implementation of a publisher and a subscriber in ROS Noetic.   In this example, we have considered the following: Example 1:  One publisher (pub.py) and one Subscriber (Sub.py) Topic: first_lecture Message: String Message  Example 2: Two publishers (pub.py and pub1.py) and Two subscribers (sub.py and sub1.py) Topic: first_lecture   See the following video for step by step instructions for running this example: The following picture shows the nodes (The picture is taken by running the rqt_graph command) Publisher Subscriber in ROS Noetic How to run in ROS Noetic Prerequsities  1. Ubuntu Basic commands 2. PATH Setting in Ubuntu 3. Basic knowledge of Linux  4. Programming fundamentals To Install ROS1 Noetic in Ubuntu 20.04, you can refer the following video in my channel. ROS is enabled with a catkin make system which perform the easier build operation and cross compilation enablement. Create a workspace to store all

Telnet and FTP for a Wired Networks This post tells about the use of Telnet and FTP in Network Simulator 2 for a wired network. This can be extended to a wireless network as well. The following is the source code for implementing Telnet and FTP application in a Wired network scenario.  The network looks like this: Telnet in NS2 Node 0 to Node 2 is enabled with Telnet Application and Node 1 to Node 3 is enabled with FTP Application.  Save the following file as wired.tcl #=================================== # Simulation parameters setup #=================================== set val(stop) 10.0 ;# time of simulation end #=================================== # Initialization #=================================== #Create a ns simulator set ns [new Simulator] #Open the NS trace file set tracefile [open out.tr w] $ns trace-all $tracefile #Open the NAM trace file set namfile [open out.nam w] $ns namtrace-all $namfile #=================================== # Nodes

ROS Noetic Installation Today we are going to see the installation of  Robotic Operating System 1 (ROS) Step 1: What We need: This will mainly work on Ubuntu 20.04 OS  Support till 2025 May. Name of the ROS: Noetic  For the complete installation step by step, you can watch the video given below Step 2: Commands Here are the commands to be used one after the other.  $ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list' $ sudo apt install curl # if you haven't already installed curl $ curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo apt-key add - The above commands add the ROS to the aptitude manager and we can now install ROS1 with simple commands $ sudo apt update $ sudo apt install build-essential autoconf automake libxmu-dev $ sudo apt install ros-noetic-desktop-full The above command need 370MB of softwares to be downloaded. So the complete package of ROS in

Constrained Application Protocol using Node JS Constrained application protocol is shortly called as CoAP and its based on Request Response Model where a browser or application will be requesting for a resource from the server. The resource would be a sensor reading like temperature, humidity, heartbeat, etc.  For complete explanation of the source code and the demo please go through the video: CoAP can be developed with many programming or scripting languages like: Python Node JS Contiki OS In this article, I will be writing or explaining the source code of CoAP using Node JS and this can be demonstrated with a plugin name called Cu Plugin for Chrome Browser. There are many CoAP client available like coap, libcoap, etc in Linux OS and Cu Plugin being a easier and common approach for a client.  You can refer the complete This program first starts the CoAP Server and accept only the JSON format headers, else it will throw the error number '4.06'.  Based on the request URL (re

Installation of Ptolemy II in Ubuntu 22.04 This post shows the installation instructions of Ptolemy II in Windows 11 and Ubuntu 22.04 Operating System.  Ptolemy II is used to simulate and emulate discrete systems, Synchronous dataflow, dynamic Dataflow, FSM, etc. The software is free and open source and its based on Java.  The complete instructions can be found in this video  Tools needed: 1. JDK is needed (preferably JDK 11, if you have already another version of JDK, no issues you can install JDK 11 as well and you can change the runtime java based on the need. For more details on how to switch the java version in Ubuntu, Check this video ) 2. Ptolemy Software (can be downloaded from here )  Step 1: Getting ready with your Ubuntu 22.04 OS Run the following commands  $ sudo apt update  $ sudo apt install openjdk-11-jdk build-essential autoconf automake libxmu-dev Step 2 - Extract the ptolemy software through the GUI window and set the environmental variable Right click over the file

Multiple Versions of ns3 in Ubuntu 22.04 In this post, we are going to install two versions of ns3 namely ns-3.35 and ns-3.37  My OS is : Ubuntu 22.04 LTS (Long Term Support) ns-3.35 uses waf and (./waf --run scratch/first)  ns-3.37 uses cmake  (./ns3 run scratch/first.cc) So we will install both the packages  Go through the video for complete instructions To start with  $ sudo apt update  $ sudo apt install build-essential autoconf automake libxmu-dev g++ python3 python3-dev pkg-config sqlite3 cmake python3-setuptools git qtbase5-dev qtchooser qt5-qmake qtbase5-dev-tools gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar gsl-bin libgsl-dev libgslcblas0 wireshark tcpdump sqlite sqlite3 libsqlite3-dev  libxml2 libxml2-dev libc6-dev libc6-dev-i386 libclang-dev llvm-dev automake python3-pip libxml2 libxml2-dev libboost-all-dev  I have downloaded both the versions of ns3 fr