Creating Network Port Listener on Linux

Problem

I needed to test connectivity to a remote service on a particular port 443 without having to install an application that would listen on that port.

Solution

Used the nc package on linux. It was preinstalled on the ubuntu 14.04 instance that I was using in this case. If not installed apt-get install nc should do the trick.

Therefore to setup nc to list on port 443 in the background as described in this post, simply do the following as the root user:


# nc -l 443 &
[1] 3724

# netstat -anlp | grep 443
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 3724/nc 

 

References

How to Create Port Listener in Windows or Linux– Handy for Connectivity Test

 

Reinstalling Wireless Drivers Linux Mint

Problem

I could not connect to the Wifi Network after removing the old kernel images on linux mint 17.

Looks like the wifi drivers were messed. I could see the following on stdout as the linux images were being uninstalled:


-------- Uninstall Beginning --------
Module: bcmwl
Version: 6.30.223.271+bdcom
Kernel: 4.4.0-67-generic (x86_64)

Solution

The solution was to reinstall the wifi drivers:


$ sudo apt-get remove bcmwl-kernel-source

$ sudo apt-get install bcmwl-kernel-source

Check IP on Docker Image

Problem

I had a situation where one docker image with a webserver was connecting to another docker image with a MySQL server. Now couple of other docker images were added to the server and this caused an IP change on the MySQL docker image. So I needed a way to check the New IP.

Solution

Used the following to get the IP of the docker image:

# docker inspect -f '{{.Name}} - {{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $(docker ps -aq)

Once you get the IP then go to the db and then grant the webserver user and ip access to that database.

Resources

Getting a docker container’s ip address from the host

Change DNS IP Linux Mint 18

Problem

The automatic ISP DNS IP was faulty. Need to switch to another DNS server. Another problem was that Editing the resolv.conf would be overwritten.

Solution

  • Click on the Wi-fi button And select Network Connections:
Wifi Icon
Wifi Icon
Network Connections
Network Connections
  • Click on the Wifi Network you want to add the DNS addresses. From the resulting Dialogue box, click on the IPv4 Settings and add the Additional DNS servers e.g the OpenDNS IPs 208.67.220.220; 208.67.222.222 and then save:
Add DNS IPs
Add DNS IPs
  • Then Click on the Wi-Fi Icon and click on Network Settings. Then select the Preferences Icon (As shown in the screenshot below). Then Click on IPv4 and In the DNS Section Click on the Automatic ON button so that its OFF and then click Apply:
Network Settings
Network Settings

Network Preferences - IPv4 selection

Network Preferences – IPv4 selection

Network Preferences - Save Changes

Network Preferences – Save Changes

  • Finally turn of the Wifi and Turn it ON again and your changes should persist. You should be using the New DNS addresses IPs ONLY.

3 sec less Web Response Times

Research has it that a high % of users will drop a transaction if the webpage loads takes longer than 3 seconds. The distance between the user and the content is sometimes to blame.

Edge computing and caching is one of the methods content providers are employing in order to serve their users almost as if they were in the same location. At its simplest definition, it the process by which content is stored in a server that is closest to the user.

This would explain why Videos on youtube for example, load faster than those of other content providers i.e. if you are located near one of Google’s Edge Point of Presence.

Akamai’s Edge Server and Content Caching are also major players in this domain. They claim to have deployments in almost every part of the world.

Carbon60 say that they also haven’t been left behind in this race.