Controlling of IP Relay using program NetCat

Controlling of IP Relay output using command line is useful when you need switch relay on/off, for example from the another program (.bat file). Example application can be switching on the warning siren via Ethernet, when any program detected crossing of appropriate temperature, any observed parameter of gas or any similar parameter.

NetCat

NetCat is simple utility, which send data included in the file to the TCP/IP connection to the specified IP adress. This utility is distributed as freeware and can be downloaded from the home page http://netcat.sourceforge.net/ ,where you can find version for operating systems Linux, FreeBSD, NetBSD, SunOS/Solaris a MacOS X or from http://www.vulnwatch.org/netcat/ , where you can find version for Windows. Application can be used for direct sending commands to the appliance. Run NetCat.exe and by typing appropriate commands send the data (see below picture). List of all commands you can find in NetCat manual.   

In our application we create NVT command-file, which will switch on relay 1 on the IP Relay. This file we will save as “set_rel_1.bin“, and then send to IP address of IP Relay using NetCat and so we control outputs of Relay.
 

Creating of file with command

For sending command, which will switch on for example relay on the channel 1 create a file in the NetCat directory. File will only contain appropriate NVT command. Table of commands you can find in manual for appliance, but be careful commands are in binary form so you must switch your editor to HEX mode as seen in the picture below. And save it for example as “set_rel_1.bin“.

Other commands for controlling IP relay

For sending other commands (more in table) you just create file with corresponding NVT command. And then you send it in the same way.

Note: Compete list of commands will you find in manual for appliance…

Sending file to the appliance

Into the command line write the command:

nc parameters xxx.xxx.xxx.xxx yy < file name

• xxx.xxx.xxx.xxx marks an IP address of appliance you want to send data
• yy marks port on which appliance communicate
• parameters you may leave this space empty or fill it with one or more parameters
  • -d will close window with the command line
  • -n NetCat will accept only digits in IP address
  • -u connection in UDP mode instead of TCP
  • -v will write basic information about connection
  • -w will set time limit for trying to make a connection and also the network inactivity

e.g. “nc –d 192.168.1.55 23 < setrel1.bin” will send command for switching on relay on channel 1 (this command is saved in file set_rel_1.bin) to the appliance with IP address 192.168.1.55 over port 23.

Creating executable file

If you don’t want type every time command to the command line, you can create file, which will contain the appropriate text. For example “nc –d 192.168.1.55 99 < setrel1”. And save it as “filename.bat”. Executing this file will cause the same thing, as you write the command, which this file contain, into the command line.

Note: If NetCat will not do what you want let’s try NVT sequence in our application Hercules – TEST tab.