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Using netcat (nc)
25 can be replaced with the friendly value (smtp). Check error code for result or use -v option to echo output
nc -z localhost smtp && echo open || echo closed
nc -zv host protocol
netstat will list all open ports on the system, unix sockets, tcp sockets and udp sockets. the t flag limits to tcp ports the l flag limits to listening ports and the n flag disables the translation of port to service ( ie :25 displayed instead of :smtp ). then grep for the port you are interested in preceeded by a colon.
Check trough unix sockets if tcp port is open or close
Gets your IP address and has a shorter URL.
No junk, no pipe, one command, no subcommand - KISS
Why use many different utilities all piped together, when you only need two?
Nethogs groups bandwidth by process.
Requires software found at: http://lpccomp.bc.ca/remserial/
Remote [A] (with physical serial port connected to device)
./remserial -d -p 23000 -s "115200 raw" /dev/ttyS0 &
Local [B] (running the program that needs to connect to serial device)
Create a SSH tunnel to the remote server:
ssh -N -L 23000:localhost:23000 user@hostwithphysicalserialport
Use the locally tunnelled port to connect the local virtual serial port to the remote real physical port:
./remserial -d -r localhost -p 23000 -l /dev/remser1 /dev/ptmx &
Example: Running minicom on machine B using serial /dev/remser1 will actually connect you to whatever device is plugged into machine A's serial port /dev/ttyS0.
Super fast way to ftp/telnet/netcat/ssh/ping your loopback address for testing. The default route 0.0.0.0 is simply reduced to 0.
Replace 500ms by the desired delay.
To remove it: sudo tc qdisc del dev lo root netem delay 500ms
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.
no need for installing mii-tools, all generic tools
working under archlinux.
looks at html for "ip" (it's a CSS class), then a little of cut and egrep to get IPv4 address.
I use this oneliner into conky.
Flush the DNS cache under Ubuntu (Debian?)
Does a ping scan on the local subnet and returns the IPs that are up