Learning to be good at thinking, thinking, thinking.

Introduction When you encounter this problem about WebSocket connection to 'wss://<address>/live' failed: Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received, here is an article on how to fix this problem. Review According to the error message, we know that the WebSocket client s... Read More

Introduction Command nc stands for netcat, known as the swiss army knife of network tools, it’s a utility which is used for reading and writing data across TCP and UDP ports. It can be used for a lot of cool stuff, this article will take a closer look. There are two similar packages available for netcat with a slight difference between them: ... Read More

What’s up? When you use yay -S <package> to install some package and face this prompt errors occured, no packages were upgraded, don’t worry, this article will guide you to settle it down. Problem reproduce At First, let’s try to remove any local package(e.g. zoom) mannually: $ sudo rm -rf /var/lib/pacman/local/zoom-2.9.265650.0716-1/ ... Read More

What’s up? Recently, when I use yay -Syu to update the software packages, it always prompts that a package cannot be updated and prompts are warning: could not fully load metadata for package and error: failded to prepare transaction (invalid or corrupted package). It’s time to solve this annoying problem. Remove first Try to remove it firs... Read More

Table Here’s a table of the email server ports. Ports Protocal Security Authentication Description 25 SMTP None AUTH Outgoing Messages 587 SMTP None or TLS STARTTLS Outgoing Messages 465 SMTP ... Read More

Introduction Have you ever thought about setting up your own email server, but then left it behind. However, setting up a email server is not complicated. In this article, we will build it step by step from scratch. Here we will need the following environments: Nginx - an lightweight and open-source web server to offer low memory usage and... Read More

What’s up? Recently, I encountered a weird problem. When I used SSH to connect to a Linux server, the connection was immediately interrupted, and such a message appeared: free(): invalid next size (fast), screenshot as below image: Troubleshooting After that, I tried to connect using another Linux computer and still had the same problem. Bu... Read More

MD-family The MD family of hashing algorithms were designed by Ron Rivest during the late 1980’s and early 1990’s. MD actually stands for “Message Digest”. MD2 It was optimized to run on 8-bit computers and generates a 128-bit hash value the hashes are generally displayed as hexadecimal string which is 32 characters long. This hash exhibits f... Read More

Generating RSA key pair OpenSSL can generate several kinds of public/private keypairs. RSA is the most common kind of keypair generation. Generating an RSA private key You can generate a 2048-bit RSA private key with the following commands: openssl genpkey -algorithm RSA -out rsa_private.pem \ -pkeyopt rsa_keygen_bits:2048 or openssl ge... Read More

Abstract and concrete are opposite concepts, many times we just know what they mean, but don’t really understand them. So today let us get to know them again and have a clearer and deeper understanding of them. Abstract An abstract is a brief summary of one or more things, there are two important points here: From one or more things Find... Read More