Viewing TCP connections with netstat
netstat -tpn
shows TCP connections on your current machine.
Start a TCP server with nc -l 127.0.0.2 -p 12345
,
then connect to it with nc 127.0.0.2 12345
.
After this, we can see the connection:
$ sudo netstat -tpn
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.2:12345 127.0.0.1:39548 ESTABLISHED 5441/nc
tcp 0 0 127.0.0.1:39548 127.0.0.2:12345 ESTABLISHED 5445/nc
Notice our one TCP connection is listed twice!
We can see why by running strace
on netstat
:
it traverses every process in /proc
.
Tagged . All content copyright James Fisher 2018. This post is not associated with my employer.