host to host nc/tar tricks

Here are some tricks to transfer files between hosts using tar.  In the old days by habit I would just do something like (tar cvfp - ) | ( ssh host "cd /path/to" && tar xvfp - ) but here are even more simpler things, assuming you have open terminals on both hosts.

CASE 1: SENDER IS LISTENING
Here are some commands that will work; the sender command needs to be typed first then it will block until a consumer appears on the other side of the pipe.

sender% tar cvf - . | nc -l -p 1234
sender% tar cvf >(nc -l -p 1234) . # process substitution

receiver% tar xvf - < /dev/tcp/ip-of-sender/1234
receiver% tar xvf <( dd obs=10240 < /dev/tcp/ip-of-sender/1234)

The magic number 10240 is 512*20, or the default 20 512-block records of the tar command.

CASE 2. RECEIVER IS LISTENING

This is the case when you are on the receiving end and want to initiate a receive before switching over to the sending terminal.  Type the receiver command first and IO will block until there is a sender:

receiver% nc -l -p 1234 | tar xvf -

sender% tar cvf - . > /dev/tcp/host-or-ip-of-receiver/1234
sender% < /dev/tcp/host-or-ip/1234 tar cvf - .
sender% tar cvf >(cat > /dev/tcp/host-or-ip/1234) .

NOTES:
Sometimes it is necessary to add "-N" option to nc, depending on platform/distro.

Edward 20180228