How to transfer files between servers using Netcat

On linux/unix environments scp are rsyncare widely used to transfer/synchronize files between servers since they provide a secure way to transfer files between two or more computer nodes.

Quickly:

me@server1 ~ % nc -l -p 4444 < file.txt
me@server2 ~ % nc -w 3 server1 4444 > file.txt

Netcat for file transfer is extremely insecure and may only be used when security is not the concern And you have a big file. Otherwise, use scp or rsync.

Quick difference between ssh copy or rsync and netcat

If you really have to use netcat, here an example of how to do that:

Install netcat:

freebsd: pkg install netcat
redhat/centos: yum install netcat
ubuntu: apt install netcat
archlinux: pacman -S netcat

Scneario

Considering you want to transfer a file from server_1 to server_2. Or better talking in netcat way: Getting a file on server_1 from server_2:

Scenario

Transfering

From server_1, where the file “bigfile.txt” exist:

user@server1 ~ % nc -l -p 4444 < bigfile.txt

Arguments:
-l, — listen: listen mode, for inbound connects
-p, — local-port=NUM: local port number

From server_2, who will get the file from server_1:

user@server2 ~ % nc -w 3 server1 4444 > bigfile.txt

Arguments:
-w, — wait=SECS: timeout for connects and final net reads

In case you want to see the progress, install pv (pipe viewer) and add to nc command:

Please note that if netcat is installed and the nc command is not available, netcat is probably represented by ncat and/or netcat command.

Some use-cases

• You have an iso file in a dev server and would like to transfer it to another one and security is not a problem.
• You have a big system library on one dev server and would like to transfer to another one and security is not a problem.
• You don’t want to bother the dev server ssh process and you just have a simple iso file to transfer and security is not a problem.

Conclusion

Again, netcat is insecure and is not to be used as file transfer. Use it only if you have to, otherwise use scp or rsync.

References

nc(1) - Linux man page

pv(1) - Linux man page

scp(1) - Linux man page

rsync(1) - Linux man page

nc(1)