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Anonymous Platypus
Asked: 2015-03-17 00:04:48 +0800 CST

Is it possible to ping a remote Linux machine without using ssh?

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I am trying to poke/ping a remote Linux machine without using ssh. Is there any other utilities to do this?

Addition: It would be quite a lot of helpful if poke can be done without providing the remote machine's password. Is it possible?

Update: I came to know about write and wall tools. Anybody know how to use them?

ssh

2 Answers

  1. Best Answer

    knockd may be your answer.

    Server part:

    1. Install knockd --> sudo apt-get install knockd
    2. Edit configuration file --> sudo nano /etc/knockd.conf also you can use gedit or vi.

    3. The configuration file should look like this after the edit:

      [options]
        LogFile     = /var/log/knockd.log
        Interface   = wlan0
[sendMessage]
        sequence    = 1111,2222
        seq_timeout = 5
        command     = /usr/bin/env sh -c "echo 'Hello, World' | wall"
        tcpflags    = syn

      Where Interface is the listening network interface, sequence is the port knocking sequence and command is the command to be executed when knocked.

    4. Edit startup file --> sudo nano /etc/default/knockd
      In this file you only need to change START_KNOCKD=0 to START_KNOCKD=1

    5. Reload knockd to apply changes with sudo /etc/init.d/knockd reload

    Client part:

    Simply telnet in that order the server ports and the command will be executed

    telnet MYSERVER 1111
telnet MYSERVER 2222

    You can also use the knock utility:

    knock MYSERVER 1111 2222

    Final notes

    • You can also view those connections in the Logfile specified, (i.e. /var/log/knockd.log)
    • You can use a more complex port combination (i.e. 5555,5050,3333,3030)
    • You can read the entire documentation at the developer's webpage
    • You can read a great tutorial on the ubuntu community
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  2. You can try nc (netcat) to send/receive any messages (files too) over the network.

    For example the computer A has IP address 192.168.1.10 and computer B has IP address 192.168.1.20.

    At first open a port on computer A to which the computer B will connect to:

    $ nc -l 2000

    Now Computer A will listen for incoming connections on port 2000, you should use any port other than "0-1023" i.e. well known ports.

    Now we will make a connection from computer B to the port 2000 of computer A:

    $ nc 192.168.1.10 2000

    Now the computers will be connected and you can write any message from computer A which will be displayed on computer B and vice versa.

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