commandlinefu.com is the place to record those command-line gems that you return to again and again.
You can sign-in using OpenID credentials, or register a traditional username and password.
Subscribe to the feed for:
Show state of NAT, readed from '/proc/net/ip_conntrack' or '/proc/net/nf_conntrack'
See who is using a specific port. Especially when you're using AIX. In Ubuntu, for example, this can easily be seen with the netstat command.
This is also perl-less, and only uses AWK as its postprocessor. Tested with GAWK and MAWK.
if you don't do --numeric-ports, netstat will try to resolve them to names
Easy to remenber. Fot TCP only use: netstat -plant
Lists all opened sockets (not only listeners), no DNS resolution (so it's fast), the process id and the user holding the socket.
Previous samples were limiting to TCP too, this also lists UDP listeners.
Check open TCP and UDP ports
While `lsof` will work, why not use the tool designed explicitly for this job?
(If not run as root, you will only see the names of PID you own)
shell loop to scan netstat output avoiding loolback aliases (local/remote swap for local connections)
We use the "convert" command (ImageMagick package) : see man convert (http://www.ma.utexas.edu/cgi-bin/man-cgi?convert+1)
Count and Find all IP connected to my host through TCP connection.
find all computer connected to my host through TCP connection
find all computer connected to my host through TCP connection.
count connections, group by IP and port
netstat has two lines of headers:
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
Added a filter in the awk command to remove them
Useful for checking the number and state of TCP connections.