Linux - Transfer Files with Netcat behind VPN or Firewall

So, Have you ever been in a situation where you are behind a VPN or a firewall?Yes?.  If you ever are in the situation of being stuck behind a firewall or VPN connection and want to transfer a file from the machine inside the VPN or firewalled back to your local desktop.Seems Difficult? Not at all! it can be easily achieved using the netcat {nc} command. Read below for Step by Step Instructions

So, What is Netcut and why is it needed? In the simplest term, netcat is a utility that reads and writes data across the network. The netcat utility, or just nc, works on the same principle as the cat utility, but over the network. This can be very useful in a number of situations, such as testing remote services, or for use in scripts, or just to copy files over the network. The syntax for netcat is pretty simple: netcat hostname port will connect you to a server on the port specified, and allow you to send input to whatever service answers on that port. So, that's teh basic about Netcat. Now here is how to send the file over Network

On the server we’re going to pipe the output of file through cat and set netcat to listen on port 3345

# cat file-i-want-to-send.ext | nc -3345

On the desktop,  open a nc session to port 3345 and redirect the output to a local file.

# nc server.ip.address 4009 > file-i-want-to-recieve.ext

And viola! Its Done! Pretty simple!One more thing, you can verify the file is intact by doing a md5sum on the server and compare it to the one locally

On Server

# md5sum file-i-want-to-send.ext
# e4ef527eac8f5afe26d8464a963694ad file-i-want-to-send.ext

On Client

# md5sum file-i-want-to-recieve.ext
# e4ef527eac8f5afe26d8464a963694ad file-i-want-to-recieve.ext