First lets take a look at how to connect to remote system using netcat. We have 2 CentOS 7 based systems.
First install netcat on both systems

yum install nc

Start netcat on one of the systems

nc -l 4444

No connect from other system

nc remote-host 44444

Now if you type any text on one of the systems it will appear on the remote one.

Lets take a look at how to transfer data files or block level files between two remote systems.
Netcat is Unix/Linux based command that can establish connection between remote systems and write files or lets us access systems remotely. On CentOS based systems it can be installed with following command.

yum install nc

Transfer MYFILE from systema to systemb
Example 1:

On system A

nc -l 1234 > MYFILE

On system B

nc SYSTEMA 1234 < MYFILE

You just transferred the file from system to systemb via port 1234
Example 2:
On system A

cat file1.iso | nc -l 1234

On system B

nc systema 1234 > file1.iso

Disk mirroring from systema to systemb
On system A

nc -l 1234 | dd of=/dev/sdb2

On system B

dd if=/dev/sda2 | nc systema 1234

For security reasons in some cases you may want to run nc over ssh