David Melo

Limiting Concurrent TCP Connections in Rust with Tokio's Semaphore

Mon, 09 Mar 2026 00:00:00 +0000

While building a TCP server (TcpListener) in Rust, I needed to process connections one at a time. I kept noticing that new connections were being accepted but never actually processed, they just hung in standby until the client gave up and disconnected. In this post, I will walk through a minimal TCP server that uses a Semaphore to force max concurrent connections.

ESP32-C6 Deep Sleep Power Consumption with Rust

Tue, 17 Feb 2026 00:00:00 +0000

In the future, I want to start building battery powered projects, so understanding power consumption becomes critical. In this post, I will explore deep sleep power consumption on the ESP32-C6 board using Rust with Embassy and Esp-hal. Beyond simply putting the board to sleep, I’ll also examine the key factors that affect deep sleep current on this board, such as providing the correct voltage to the battery pin.

Monitor Docker containers and other systems

Mon, 05 Jan 2026 00:00:00 +0000

To keep an eye on my services and servers by monitoring how resources are being used and whether something is about to break, I took some time to explore what tools and services exist that are open-source and lightweight. I found that Beszel fits in nicely: it’s quick to deploy and easy to understand.

Read and Write Another Process’s Memory in Rust

Sat, 13 Sep 2025 00:00:00 +0000

Recently, I set out to explore how to read and write the memory of a running process in Rust. Programming isn’t just about writing code that runs—it’s also about understanding what happens under the hood. Sometimes it is necessary to understand how memory works, for debugging, or even implement a simple IPC mechanism without going through sockets or shared memory. This experiment turned into a neat experiment that combines Linux internals (process_vm_readv/process_vm_writev), unsafe Rust, and a reminder of why process isolation is such an important security boundary.

Change the default storage location of Docker Engine to an external disk

Tue, 25 Feb 2025 00:00:00 +0000

Docker’s default storage location (/var/lib/docker) can fill up quickly, especially on systems with limited space like a Raspberry Pi’s SD card. This guide walks you through installing Docker on Debian and moving its storage to an external disk for better performance and management. Let’s dive in!

Exploring Casdoor an Identity Access Management (IAM) / Single-Sign-On (SSO)

Thu, 06 Feb 2025 00:00:00 +0000

For future projects and out of personal curiosity, I want to explore authentication management platforms beyond Keycloak, which I’ve already used. In this post, I’ll take a look at Casdoor, an Identity and Access Management (IAM) and Single Sign-On (SSO) solution with a user-friendly UI, built in Go 😎. I chose Casdoor for its extensive third-party login support, customizable login themes, and a unique payment integration feature. Let’s see how it performs! 🚀

ESP32 Net Sentinel Dongle

Sun, 24 Nov 2024 00:00:00 +0000

To sharpen my Rust skills for embedded systems, I embarked on creating a project that uses Discord (and soon MQTT) to receive commands for network tasks. Users can monitor devices, perform network scans, execute pings, send WOL packets and get alerts when applications running on edge devices fail.

SVG animation

Thu, 22 Aug 2024 00:00:00 +0000

Recently, I needed to create some animated diagrams and discovered that it’s possible to animate SVG images directly within the SVG element itself. However, the process isn’t exactly straightforward. To simplify it, I decided to write this blog post to share my findings. I even developed a tool to make building SVG animations easier, which I’ll introduce as well.

Efficient Server Management: BIOS and Proxmox Automation

Thu, 01 Aug 2024 00:00:00 +0000

I am preparing a new series of blog posts about my home server setup using an old Dell Latitude 5490. This setup is designed to power on when a smart plug activates and to shut down safely when the plug turns off. To achieve this, I configured the BIOS settings (power on) and set up a cronjob for Proxmox (power off). This blog series will cover these configurations and the overall process.

Use a Sonoff as Dry Contact relay

Wed, 01 May 2024 00:00:00 +0000

Here at home, we lost all the garage door remotes. Since I had a spare Sonoff RFR3 lying around, I decided to modify it to be able to activate the garage button. But to do that, I had to make some modifications, as you’ll see later in this blog post.

Managing Docker Containers on Edge Devices with Portainer

Sun, 04 Feb 2024 00:00:00 +0000

Imagine having multiple devices running Docker containers. How do you effectively manage all these containers? Personally, I’ve found the solution with Portainer. I can have a master running the main program and multiple agents running on the devices. In this blog post, I will explain various setups that are possible.

Firebase + Vite: Push Notifications Simplified

Sun, 07 Jan 2024 00:00:00 +0000

I wanted to explore the process of sending server messages to PWA apps. In this blog post, I will guide you through the steps I took to set up this functionality using Vite.

Mosquitto passwd generator

Sun, 05 Nov 2023 00:00:00 +0000

Mosquitto, one of the widely used MQTT brokers, offers robust user authentication through username and password combinations. However, creating password files using the official terminal tool ‘mosquitto_passwd’ can be a challenging task. To address this issue, I have developed an online tool that simplifies this process, making it more accessible and user-friendly.

Receive MQTT messages in your browser and send commands to serial devices

Sat, 28 Oct 2023 00:00:00 +0000

Use your web browser to connect to an MQTT broker and create alerts based on the messages that you receive. It is also possible to connect to a serial device and send commands (e.g., make an LED blink) based on the alerts that you created. Another feature is the ability to receive messages from a serial device and publish these messages to a specific topic with the help of a JavaScript decoder.

CloudFlare DNS Service as a Dynamic DNS Provider (DDNS)

Sat, 23 Sep 2023 00:00:00 +0000

This week, I switched to a different telecommunications provider, which led to a dynamic public IP address. Consequently, in today’s blog post, I will discuss the implementation of CloudFlare DNS Service as a Dynamic DNS provider. This configuration ensures that services hosted on the home network remain accessible to remote users through a stable and automatically updated domain name.

Creating the ideal development environment for ESP32 boards

Sun, 17 Sep 2023 00:00:00 +0000

Today I will share my journey of preparing a working environment to develop Rust for Espressif boards. Discover how I made the decision to work with Rust for embedded systems, a language known for its safety, speed, and reliability. I’ll also guide you through the process of preparing your development environment, like installing necessary tools, and configuring your workspace to program Rust in VS Code using Docker Dev Containers.

PocketBase Piggy Bank

Wed, 10 May 2023 00:00:00 +0000

PocketBase is an open source Go backend that features an embedded database and an admin dashboard UI. As part of this project, I developed an app to manage a piggy bank associated with the sale of products. With this app the users can register how many products they bought and also register the amount they left (charge) in the piggy bank by indicating the amount and taking a photo as proof.

Arduino SerialPort GUI built with Electron + Vue

Sun, 19 Mar 2023 00:00:00 +0000

Have you ever wanted to control or configure an Arduino board using a user-friendly graphical interface? In this blog post, I will explain how to build a GUI with Electron (a popular framework for building cross-platform desktop applications) and Vue. With this application, you’ll be able to list Serial Devices and easily send data to an Arduino with a click of a button.

My home VPN server setup

Sun, 05 Mar 2023 00:00:00 +0000

In today’s digital age, many of us have smart devices or applications at home, but how can we access them from anywhere in the world without exposing them to potential threats? The answer is: with a VPN! A home VPN not only provides a secure and encrypted connection, but also allows us to access our home network, files, and devices remotely. In this blog post, I will share my home VPN setup and also explain how to use a DNS server to identify devices and applications using domain names instead of IP addresses.

Influxdb + Telegraf + MQTT - docker-compose

Sat, 11 Feb 2023 00:00:00 +0000

Let’s assume that we have a lot of sensors publishing structured data to an MQTT broker and we want to store this data in a database. A simple way to do that is to use Telegraf (tool from InfluxData) to consume and process the data and store it in an InfluxDB database. In this tutorial, I will explain how to prepare this setup using docker-compose.

Redis TimeSeries + Go + gRPC + Vue

Fri, 20 Jan 2023 00:00:00 +0000

This post is complementary to the previous post of Redis TimeSeries, in which I explained the benefits of using Redis to store time series data. In comparison, instead of using Grafana to plot the data directly from Redis I will explore using gRPC-web to establish a connection between the backend written in Go and the frontend application written in Vue.

Redis TimeSeries + Go: Structs to Key Values

Tue, 10 Jan 2023 00:00:00 +0000

Most of you know Redis as a key-value database, but did you know there is a module that simplifies the use of Redis for time series use cases? In this post I will explain a simple way to store time series data in Redis using Go and visualize it in Grafana. The Go script is designed to be easily adaptable to new use cases, like using a Raspberry Pi to save system metrics (it will reduce the number of write cycles in SD card because the data will be stored in RAM).

Docker + Port Scraper

Tue, 20 Dec 2022 00:00:00 +0000

This post is part of a series of a simple networking scanning tool named PortScraper. I will explain how to embed the application into Docker image and how to prepare the setup (PortScraper + MariaDB) with docker-compose.

Port Scraper

Tue, 13 Dec 2022 00:00:00 +0000

I created this post to explain to you the steps that I did to setup a simple tool to scan a huge range of IPs and store the results in a MYSQL database using Go.

Mon, 01 Jan 0001 00:00:00 +0000

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