nc and tar play nice then

2011-11-08 09:20

Convenience transfer file with nc, just like:
receiver:

 nc -l -p 2000 > filename

sender:

 cat filename | nc 192.168.1.1 2000

It is working fine for single file.

Tar archiving also convenience too.
pack:

 tar c .

extract:

 tar x

Combine them together, seem not work fine.
receiver

 nc -l -p 2000 | tar x

sender

 tar c .  | nc 192.168.1.1 2000

I think the reason is tar result is block by block, and there is nothing mean EOF, so tar x never know when to close the pipe.

I also found #1 use cpio, tar - even not work fine. I tried rsync -e, either not work.

A geek nearby provide a solution: tar -ix
in man tar:

-i, --ignore-zeros
             ignore blocks of zeros in archive (normally mean EOF)

It work perfect.
receiver

 nc -l -p 2000 | tar -ix

sender

 tar c .  | nc 192.168.1.1 2000

TODO: read source code of tar, find out what zero blocks really mean.

[1] http://ask.metafilter.com/133905/Why-did-tar-and-nc-not-play-nice