Commands tagged protocol (3)

  • this command will send a message to the socket 25 on host 192.168.1.2 in tcp. works on udp and icmp understand only IP address, not hostname. on the other side (192.168.1.2), you can listen to this socket and test if you receive the message. easy to diagnose a firewall problem or not.


    25
    echo "foo" > /dev/tcp/192.168.1.2/25
    mobidyc · 2009-09-12 16:48:05 3
  • Using netcat, usuallly installed on debian/ubuntu. Also to test against a sample server the following two commands may help echo got milk? | netcat -l -p 25 python -c "import SocketServer; SocketServer.BaseRequestHandler.handle = lambda self: self.request.send('got milk?\n'); SocketServer.TCPServer(('0.0.0.0', 25), SocketServer.BaseRequestHandler).serve_forever()" Show Sample Output


    2
    echo foo | netcat 192.168.1.2 25
    pykler · 2009-09-13 01:33:02 0
  • you can use a pair of commands to test firewalls. 1st launch this command at destination machine ncat -l [-u] [port] | cat then use this command at source machine to test remote port echo foo | ncat [-u] [ip address] [port] First command will listen at specified port. It will listen TCP. If you use -u option will listen UDP. Second command will send "foo" through ncat and will reach defined IP and port. Show Sample Output


    -1
    echo foo | ncat [ip address] [port]
    dragonauta · 2012-10-26 10:53:47 0

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