Nginx 80 is blocked in Oracle Cloud Server?

The Oracle Always Free plan is an excellent option, but I found myself struggling with their firewall settings while attempting to run an Nginx web server. Despite enabling port 80 in both the network security groups and security lists, it was still being blocked for unknown reasons.

Firstly I checked the ufw settings and it was disabled definitely. However, when I looked at the iptable rules by executing sudo iptables -L, I was surprised by lots of existing rules there.

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Spawn Objects in Gazebo of ROS Kinetic & Melodic (Python 2.7)

Spawn objects in the TIAGO’s gripper

Sometimes we need to add new objects to Gazebo to build a dynamic environment, particularly in some manipulation tasks. Suppose we test if the robot can pick up items from the floor. Thus, we may need a program to spawn models in a random position in the environment to verify our manipulation algorithms’ robustness. Like the top picture, a new cylinder is created in TIAGO’s gripper. Then TIAGO can deliver the cylinder to a free container.

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macOS GPU Fan spins wildly

Some PCIe GPU fans spin uncontrollably on macOS computers, and it is very annoying to hear these fans’ buzzing. My computer is built with a Radeon RX 570 and sometimes has the above fan issue, especially after booting.

I searched the internet and found a tricky solution (source) that to install a benchmark software called LuxMark. After opening this software and running for a few seconds, the graphics card fan will magically return to the normal speed.

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Socks5 Proxy Scheme with Remote DNS resolving

When using a Socks proxy, you must have written a string like socks5:// to represent the proxy protocol and address. Strings in this format are widely used in CURL based components such as Guzzle, pip, and urllib3. We often want these programs to use a Socks proxy to connect to the internet but get weird connection failures. An interesting part of these strange failures is that accessing some websites works fine, while others cannot. These failures persist even if you have confirmed that there is no failure of the proxy connection itself. At this time, I suggest you consider that these failures are caused by DNS issues, especially when you are in some special network environment, such as the network affected by DNS pollution, the Great Firewall of China or a public WIFI.

We know that the Socks proxy works at the session layer and can forward TCP connections. Furthermore, Socks4a and Socks5 support DNS forwarding. Now, the most commonly used version is Socks5. Let’s take a careful look at the proxy protocol string. The reason for the DNS resolution error is that when we use addresses starting with socks4:// or socks5://, which means the hostname will be resolved locally and get unexpected results. The local resolving is not an actual error or bug. It is a critical feature in some cases. But when you are in a restricted network, your local DNS may be polluted or unavailable. You need to change your protocol prefix to socks4a:// or socks5h://, which means the hostname will be resolved by the proxy server.

This is a problem can be solved by a simple answer and in fact well-defined in the CURL documentation. But most tutorials usually only provide a string like socks5:// to tell the user how to apply a Socks5 proxy. And access failures caused by DNS are often difficult to recognize and locate. Even if users know that the failure is related to DNS, it is more difficult to search for relevant answers in Google. You can find some discussions like and

Overall, try to use socks5h:// or socks4a:// in your proxy settings when you face some strange access failures. Hope that is helpful for you!