Part of the problem with trying to learn some of this on your own is that you miss the basics.
I'm reading through a TCP tutorial, and I'm hoping someone can help me understand a few things (or point me in the right direction).

"The first frame shows the FTP client sending a control frame to the FTP server. The control connection port number is 1183, making the data connection port number 21. The port number 1184 (FTP command) is calculated in the FTP header. You will understand where these port numbers fit in the whole scheme of things as you follow this trace.

Frame Source Address Dest. Address Summary
1 [192.168.10.4] [192.168.10.5] FTP: C PORT=1183 PORT 192,168,10,4,4,160"


C PORT 1183=port 21? Is there a table that one follows for that? Or in other words, how does 1183=21?


"
This will define the TCP file transfer connection port number. The first four comma-delimited numbers represent the IP address. This is where it gets interesting: The last 2 numbers (4, 160) are numbers inserted in a simple equation calculating the data connection port number that will be used to transfer the requested file.

4 x 256 + 160 = 1184. Watch for port 1184 in the next few frames. "

Do the last 2 numbers in the sequence always designate the port number? Why is it multiplied by 256, and not, say, 128?

I think what is confusing me is the 3 different port designations. Would anyone be kind enough to help me clear up my brain fog?

Thanks