Understanding TCP problems is sometimes quite complex. The best way to do it, most of the time, is to use graphical software that has a better graphical interface, or simply take a piece of paper and different colored pens and draw it yourself.

Friendly software that can do the job includes the Cascade Pilot package from the developers of Wireshark: http://www.riverbed.com/us/products/cascade/wireshark_enhancements/cascade_pilot_personal_edition.php.

You can see an example of a self-made graph in the following diagram:

You can clearly see how a TCP connection is set (frames 2-4), how the client 10.0.0.5 sends the HTTP POST command and gets 200 (OK) from the server 77.234.41.58 (frames 5-7), and how a connection is orderly closed (frames 8-11).

We will see more of these self-made graphs later in Chapter 12, FTP, HTTP/1, and HTTP/2, and in other applications chapters. After a few graphs, you will know this like the back of your hand.