netcat proxy shell issue on linux

Question

I am trying to follow a number of recipes which use netcat or ideally knc (kerberos netcat) to create a proxy; either to look at what is being piped through the proxy for debugging or to create an kerberos authenticated link over which I can tunnel some java based tcp server-to-server traffic.

Taking this example http://notes.tweakblogs.net/blog/7955/using-netcat-to-build-a-simple-tcp-proxy-in-linux.html the pattern seems to be something like:

mkfifo fifo
nc -l -p 8080 <fifo | nc tweakers.net 80 >fifo

Yet that gives the error:

usage: nc [-46DdhklnrStUuvzC] [-i interval] [-p source_port]
          [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]
          [-x proxy_address[:port]] [hostname] [port[s]]

Yet if I run ether side of the pipe alone I get no error:

nc -l -p 8080 <fifo
nc tweakers.net 80 >fifo

What am I missing to get this to work?

I am running Red Hat Enterprise Linux Server release 6.2 (Santiago) either bash or ksh.

simbo1905 · Accepted Answer · 2013-07-18 17:50:19Z

3

Annoyingly it was the -p option which was tripping things up. The following command runs fine:

nc -l 8080 <fifo | nc somehost.com 80 >fifo

Then in another shell doing

telnet localhost 8080
get /

works fine.

answered Jul 18, 2013 at 17:50

simbo1905

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