tcpdump and tftp command

1. Window TFTP Command
tftp -i [IP ADD] [PUT|GET][ FILE NAME]
-g:     get file
 -r:     remote
 -p:     put file
  -l:     local

tftp -i 192.168.1.55 PUT test.txt

2. TFTP Linux
Example: 

tftp [-g|-p]  -r FILENAME SERVERIP

Download: 

tftp -g -r tcpdump 192.168.1.50

Upload

example: tftp -p -r test.txt 192.168.1.50

3. TCPdump and tftp Command, doing packet capture under ROUTER 
You can do this on linux PC also 

Capture all packet:

#cd /var/tmp

#tcpdump -nni any

Capture wan0 interface 

tcpdump -i wan0 -s 0 -w wan0.pcap&

stop capture packet, kill process id

#ps |grep .pcap

#kill -s tcpdum 'pid'

upload to your pc by tftp command

tftp -l wan0.pcap -p 192.168.1.50