tcpdump(8) tcp port 3389 -i eth0 -vvX -w 'rdp.%FT%H-%M-%S.pcap' -C 500 -G 86400 -W 10
dump traffic on a network
-i     Listen on interface.  If unspecified, tcpdump searches the system interface list  for  the  lowest
       numbered,  configured up interface (excluding loopback).  Ties are broken by choosing the earliest

       On Linux systems with 2.2 or later kernels, an interface  argument  of  ``any''  can  be  used  to
       capture packets from all interfaces.  Note that captures on the ``any'' device will not be done in
       promiscuous mode.

       If the -D flag is supported, an interface number as printed by  that  flag  can  be  used  as  the
       interface argument.
-v     When parsing and printing, produce (slightly more) verbose output.  For example, the time to live,
       identification, total length and options in an IP packet are  printed.   Also  enables  additional
       packet integrity checks such as verifying the IP and ICMP header checksum.

       When  writing  to  a  file  with  the  -w  option, report, every 10 seconds, the number of packets
-X     When parsing and printing, in addition to printing the headers of each packet, print the  data  of
       each  packet (minus its link level header) in hex and ASCII.  This is very handy for analysing new
-w     Write the raw packets to file rather than parsing and  printing  them  out.   They  can  later  be
       printed with the -r option.  Standard output is used if file is ``-''.  See pcap-savefile(5) for a
       description of the file format.
-C     Before  writing  a  raw  packet  to  a  savefile,  check whether the file is currently larger than
       file_size and, if so, close the current savefile and open a new one.  Savefiles  after  the  first
       savefile  will have the name specified with the -w flag, with a number after it, starting at 1 and
       continuing upward.  The units of file_size are millions of bytes (1,000,000 bytes,  not  1,048,576
-G     If specified, rotates the dump file specified with the -w  option  every  rotate_seconds  seconds.
       Savefiles  will  have  the  name  specified by -w which should include a time format as defined by
       strftime(3).  If no time format is specified, each new file will overwrite the previous.

       If used in conjunction with the -C option, filenames will take the form of `file<count>'.
-W     Used in conjunction with the -C option, this will  limit  the  number  of  files  created  to  the
       specified  number,  and  begin  overwriting  files  from the beginning, thus creating a 'rotating'
       buffer.  In addition, it will name the files with enough leading 0s to support the maximum  number
       of files, allowing them to sort correctly.

       Used  in conjunction with the -G option, this will limit the number of rotated dump files that get
       created, exiting with status 0 when reaching the limit. If used with -C as well, the behavior will
       result in cyclical files per timeslice.
source manpages: tcpdump