Google said
lsof
-i [i] selects the listing of files any of whose Internet address
matches the address specified in i. If no address is
specified, this option selects the listing of all Internet
and x.25 (HP-UX) network files.
I have the following output
root@Landau:~# lsof -i:8018
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
celery 1843030 root 10u IPv4 49086348 0t0 TCP Landau.site.ru:58490->Landau.site.ru:8018 (ESTABLISHED)
python 1941119 root 3u IPv4 48907368 0t0 TCP *:8018 (LISTEN)
python 1941119 root 4u IPv4 49092801 0t0 TCP Landau.site.ru:8018->ppp83-237-176-131.pppoe.mtu-net.ru:14800 (ESTABLISHED)
The second line is my process (listening on 8018)
What does it mean -> and ESTABLISED?
The question you asked is:
What does it mean ->
It lists that the host:port on left side of -> is connected to host:port on the right side of ->. For example, host Landau.site.ru host has connected from port 8018 to host ppp83-237-176-131.pppoe.mtu-net.ru to port 14800.
and ESTABLISED?
It means that the actual TCP connection has been made, SYN -> SYN-ACK -> ACK messages exchanged, and the connection can be used (or, well, is used) to transmit messages.