If you are using FTP server with ssl/tls support you must know that only a few ftp clients

(namely free ones) have the support for secure file transfers.

 

 

 If you run a more or less loaded apache web server, you will sooner or later happend to be in a situation that you need to know what ips are currently connected.  

 

Here's when netstat command comes in very handy.

To list all connections just issue:

 

Since apache uses TCP we can limit the output to TCP connection:

 

and we eliminate the dns lookup time overhead by adding another flag:

Ok, this will list all the tcp connections. Next we want to only list connections belonging  to apache. Apache's binnary is called httpd and netstat with -p parameter will list socket owner's process number and process name.

 

 

Now we have all sockets owned by apache. The problem is, that not all of them belong to currently connected users. We need to filter out only ESTABLISHED connections.

 

 

Ok, almost there - now we use the cut utility to get only remote ips connected:

 netstat -anpt|grep httpd|grep ESTABLISHED|cut -b45-60|cut -d':' -f1

 

Now we have only remote ips, but it can be a pretty long list and there will be duplicit ips listed. We will use uniq and sort commands to sort it by number of occurences of remote ip address:

 

 

If you wonder why there are 2 sorts - the first one is neccessary for uniq to filter out same lines, the second one orders the whole thing by number of ip occurences given by the output of uniq -c command.

 

Now you have nice sorted list of ips connecting to your web server at the current moment. Using watch command you can monitor the output for a longer time:

 

 

 

 

 

 

 

 

Xvfb acts like a normal X server, but insted of writing the output to the graphics adapter, it writes the graphical output in a binary format into memory. This gives us the opportunity to capture any window running at the Xvfb DISPLAY.

 

Xvfb is included in standard Xorg installations and can be run with a couple of basic parameters.

 

Xvfb :1 -screen 0 1400x2000x24

 

This tells the Xvfb to run on DISPLAY number 1 and screen number 0 with resolution width of 1400 and height 2000 in 24 bit color depth. 

 

 Now we can capture the screen of any window running in the Xvfb DISPLAY/screen with xwd utility.

We have to tell the xwd which screen to capture by either setting the DISPLAY environment variable:

export DISPLAY=:1.0 

 

or by adding a -display and -screen parameters to the xwd tool. Taking the first approach we issue:

 

 

 Now we have a binary file screen.xwd. In order to convert the xwd file to more convenient format we have 2 utilities - xwdtopnm and pnmtojpeg. The first converts the xwd to pnm and the second from pnm to jpeg image format. 

 

Now to put it all together: 

 

xwd -root -silent | xwdtopnm |pnmtojpeg > screen.jpg