Using linux as the basis for complex testing systems I quite often 
have to create applications talking to devices like measurement 
instruments or RFID controllers via IP based network connections. As in the 
days of RS232/423/485, many of those devices like to communicate using their 
very own very special protocol containing control characters, checksums, 
size informations … at some place within the data.

Additionally device documentations are not always distinct and sometimes 
erroneous, too.

Therefore it is a good idea to test communications using an universal tool 
before creating the application. For serially connected devices (yes, there
are still some out there) I am very happy with Moserial, 
but could not find anything similar for networked devices. One might consider 
to use ncat, and I did, too, in the past. 
You can send every character with ncat, but receiving control characters is 
dissatisfying.

Thus I decided to write a tool of my own, very minimalistic, just with basic 
functionality and created hexnet.

Hexnet is a console based appliction for testing of binary communications. It
accepts multiple pairs of characters interpreting each pair as a hexadecimal
number.
Pairs may optionally be delimited by any character, e.g. "2a:45" or "44 4c".
Lower and upper case letters are both accepted.

Data is send to a host specified by IP address and port, received data can be
displayed in different formats.

• Download and unpack hexnet-1.1.1.tar.gz.
• Change to directoy hexnet-1.1.1.
• Compile
  As I provide neither a Makefile nor any autotools compliant files, you need to call
  the compiler directly:

        gcc -O2 -Wall -c cmdline.c hexnet.c hexnetfunctions.c

• Link
  Call the compiler to link the object files:

        gcc -O2 -Wall -o hexnet cmdline.o hexnet.o hexnetfunctions.o

• Install
  Install the hexnet executable and man page, e.g.:

        install -v -m755 hexnet /usr/bin/
        install -v -m644 hexnet.1 /usr/share/man/man/

• Set up ncat invoking a shell in one terminal:

        ncat -l 127.0.0.1 8888 --sh-exec "/bin/sh" --keep-open

• Start hexnet in a different terminal:

        hexnet -a "127.0.0.1" -p 8888  -m 256 -f0

• Execute pwd by hexnet and watch the output:

        70 77 64 0a

• Kill hexnet (^C) and start again with a different output format:

        hexnet -a "127.0.0.1" -p 8888  -m 256 -f2

• Execute pwd by hexnet again:

        70 77 64 0a

Hexnet is provided "as it is", currently I do not plan to add any features.
However, this might happen from time to time. Current release is 
hexnet-1.1.1.tar.gz, the original one can be found here.

Hexnet is released under GPL3, so feel free …
If you find any bugs, you might contact me:

        the.druid[at]arcor.de