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How to setup 2FA On Linux SSH Login

  This is a simple setup guide to enabling Two Factor Authentication (2FA) on Linux SSH login. I this article I wont go deep into setup and issues that I have faced when implementing this. First thing is first Update your system first. I have used Ubuntu 20.04 and it is always up to date. To enable 2FA you need to install google authenticator modules sudo apt install libpam-google-authenticator Configuration for PAM and SSHD Add the the following line to /etc/pam.d/sshd and After adding this line please restart the sshd services.  auth required pam_google_authenticator.so Go to /etc/ssh/sshd_config and check if the following line exist. Default value will be "no" so change it to "yes" to activate.  ChallengeResponseAuthentication yes Configuration for Authenticator In the terminal run google authenticator command It will ask few things to acknowledge by user. Details you can see from the below video. Once this part is done you are ready to use the 2FA in ubuntu. T...
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SIM900A TCP connection test - 1

I have been working on some real time data acquisition and control application designing. Specially micro-controller based hardware designing and prototyping.
For testing purposes i am using SIM900A GSM/GPRS module and FTDI UART converter. 

SIM900A module is connected to PC via FTDI converter. I use putty as a terminal program to communicate with the module. With required baud rates i am able to communicate with the module by sending a simple AT command (AT command set will vary with different modules) just sending AT the module replies with OK. This means module responded to the command sent from PC. Lets go ahead with TCP AT commands to establish a TCP connection to remote server via GPRS connection.


I have run socket test software on remote PC and opened port 7777. You have to check your firewall or router settings to allow your preferred port. While the software start listening to port 7777, lets continue with the sending AT commands to module from the PC connected to module.

After power up the module please wait for a while to give time to connect to GSM network from module and after few seconds lets proceed with TCP.

I have send these few commands manually from the PC which the module is connected.

AT+CIPMUX=0
AT+CIPMODE=0
AT+CGATT?
AT+CSTT="APN of pixelatedpic"
AT+CIICR
AT+CIFSR
AT+CIPSTART="TCP","remote pc/server IP ","your preferred port"
AT+CIPSEND=20 
your data to send and hit ENTER


Here is the data sent between module and sever via GPRS internet. The data transmission of both directions is successful. Next is try to send the AT commands from Arduino instead of doing manually.

I love to see more comments from the viewers.
stay tune for part 2.

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