Terminal escape character for hexadecimal input

Question

In my usual gnome-terminal I do a

netcat -u somewhere 1234

to start sending UDP packets to somewhere. I need to transmit the following 5 bytes, written in hexadecimal: "01 00 af 0f e1". Now how do I type a escape sequence into my terminal that causes it to send these exact 5 bytes to stdin of netcat?

Update: Just to clarify. I know several ways of actually inputting the bytes I want to the program. That is not the question. The question is what sequence of keystrokes do I type into my terminal, after the program is launched, to input a hexadecimal character that is not otherwise represented on my keyboard. (Such as 0x00, 0x01, or 0x0f.)

I am starting to think it is simply not possible, however I would be a bit surprised if that is the conclusion.

Answer 1

You can use echo -e, (which is what I think richardhoskins meant.) Like this:

/bin/echo -n -e "\x01\x00\xaf\x0f\xe1" | netcat -u somewhere 1234
# -n: no newline at end, -e: interpret escapes

If your echo implementation is old, (or simply not GNU-encrusted,) the old-school way is to use octal:

/bin/echo -n -e "\001\000\257\017\341" | netcat -u somewhere 1234

Yes, octal is way, way old-school. Look at ibase and obase in the man for bc. Check to see if echo does the right thing with od ("octal dump") "od -tx1" for hex, "od -to1" for octal.

Answer 2

A simple approach, though not quite what you are looking for...

Use a hex editor to create a file with the bytes in that you want to send (you mention gnome so you may already have ghex but any hex editor should be fine). For short hex sequences I usually include the hex as part of the name (e.g. test0x0100af0fe1).

Then just redirect the content into netcat, e.g.:

mas@voco:~$ nc -o testout 127.0.1.1 80 < test0x0100af0fe1
^C
mas@voco:~$ cat testout
> 00000000 01 00 af 0e 10                                  # .....
mas@voco:~$

This has the disadvantage of having to prepare a separate file but it makes replication and documentation of tests easier.

Answer 3

Append \x to the beginning of the byte. e.g. "\x01 \x00 \xaf \x0f \xe1".

Answer 4

you have to use perl in terminal example:

./program perl -e' print "\x41\x60\x34\x45"'

it will send this hex address to program. It is used often in buffer overrun as hexa address input. The page does not show everything I typed. Look on google for buffer overflow. Those pages show you everything. Here are missing back single quotes in front of perl one and second at the end of a whole input.