1 Examples of tcpick usage

1.1 connection status

Tcpick is a sniffer able to understand wich status has the connection (SYN-SENT, SYN-RECEIVED and so on). To see the connection tracker in action on eth0 simply type:

     # tcpick -i eth0 -C

`-C' means “enable colors”, and the output is very pretty.

You will see something like this:

     23:07:42.672171  1      SYN-SENT >
     23:07:42.822239  2      SYN-SENT >
     23:07:42.826634  3      SYN-SENT >
     23:07:42.854681  4      SYN-SENT >
     23:07:43.084242  1      SYN-RECEIVED >
     23:07:43.087045  1      ESTABLISHED >
     23:07:44.061311  5      SYN-SENT >

1.2 display the payload and packet headers

It is very easy:

     # tcpick -i eth0 -C -yP -h -a

`-yP' means “payload printable”, `-h' means “header” and `-a' means names resolution. Unprintable carachters are displayed as dots.

1.3 display client data only of the first smtp connection

     # tcpick -i eth0 -C -bCU -T1 "port 25"

`-bCU' means: display the rebuilded stream (`-b') only the client side (`C') and unprintable carachters will be displayed as hexcode (`U').

`T1' means: display only the first (1) connection.

“port 25” is the filter.

1.4 download a file passively

Yeah! It is very a simple job:

#tcpick -i eth0 -wR “port ftp-data”

When the file has been completely transmitted (connection displayed as “CLOSED”) check in the working directory: you will find some files named like this:

     # ls *.tcpick

Bingo! If you do `$ file *.tcpick' you will find that one of the two is a a gzip archive or whatever you sniffed.

1.5 redirect the first connection to a software

You must choose between client or server side, because you don't want both stream mixed in the standard output. It is a really simple job, just type:

     # tcpick -i eth0 --pipe client "port 80" | gzip > http_response.gz


     # tcpick -i eth0 --pipe server "port 25" | nc foobar.net 25

Now, use your imagination and let me know what crazy experiments have you done with tcpick ;^)