38
votes
What's the easiest way to find an unused local port?
One-liner
I've put together a nice one-liner that quickly serves the purpose, allowing to grab an arbitrary number of ports in an arbitrary range (here it's divided in 4 lines for readability):
comm ...
- 489
22
votes
Accepted
reading TCP connection list from /proc
There are many misunderstandings in your approach. I'll go over them one by one.
Sockets are not associated with a specific process. When a socket is created its reference count is 1. But through ...
- 3,680
18
votes
Accepted
Is there documentation for /proc/net/netstat and /proc/net/snmp?
The /proc/net/* files are generated by the kernel: the entries are in net/ipv4/proc.c in the kernel source, and the entry list is found in include/uapi/linux/snmp.h. It grabs the values from various ...
- 4,207
14
votes
Accepted
Why is netstat deprecated?
Found an article on deprecation from 2011. It seems like the whole net-tools package was not maintained for a while and so it was deprecated. In Debian 9 it is not even installed by default. From the ...
- 1,128
13
votes
How to figure out the meaning behind Recv-Q and Send-Q from netstat?
tcp 8216172 0 127.0.0.1:9503 127.0.0.1:47654 ESTABLISHED 34390/python
means that process 34390 has a connection open, between port 9503 on the local host, and port 47654 on the local host, and that ...
- 481k
11
votes
Accepted
Given a service name, get its port number?
There are two standard library calls; getservbyname(3) and getservbyport(3). These allow programs to convert a name (e.g. telnet) to a port (23), or from a port back to a name.
The typical ...
- 49.3k
10
votes
chromium browser (pepperflashplugin) opening listening ports on 0.0.0.0:5353
To disable mDNS and SSDP you now have to set up a policy. The browser looks for a policy config file in the following directory:
Google Chrome: /etc/opt/chrome/policies
Chromium: /etc/chromium/...
- 148
9
votes
port being in use not displayed in netstat output
Just had a similar case on Ubuntu 14.04. Indeed jenkins default port (8080) is mapped to "http-alt" name in /etc/services. You can easily check this with
grep 8080 /etc/services
http-alt 8080/tcp ...
- 313
9
votes
Incoming and outgoing traffic when NOTHING is running
Those packets you are seeing are regular multicast services (and while the process is similar to broadcast packets, they are not broadcasts per se); their output traffic in the network is also (...
- 58k
8
votes
Accepted
What is this : ^[3;J^[H^[2J?
It is the output of the clear command …
You ran clear. clear produced these control sequences. (They are merely in a different order on my machine.) % clear | cat -v ; echo
^[[2J^[[H^[[3J
%
...
- 71.9k
7
votes
Finding the PID of the process using a specific port?
I'm working on a Yocto Linux system that has a limited set of available Linux tools. I managed to find the process of a running port using the following commands (where I find the process using port ...
- 2,505
7
votes
What's the easiest way to find an unused local port?
This is the version I use:
while
port=$(shuf -n 1 -i 49152-65535)
netstat -atun | grep -q "$port"
do
continue
done
echo "$port"
The command shuf -n 1 -i 49152-65535 gives you a "random" port ...
- 73
7
votes
Accepted
What does address 224.0.0.251:5353 represent?
224.0.0.251 is Multicast DNS, and it use the port 5353 (as you noticed). Many operating systems use it to discover new devices/printers/routers with zero or nearly zero configuration. E.g. if you want ...
- 3,031
5
votes
Accepted
Netstat doesn't show my machine IP as listening on port 22
You machine is listening to port 22. Here's the line:
tcp6 0 0 :::22 :::* LISTEN
The socket is listening for both IPv6 and IPv4 connections.
- 13.7k
5
votes
Accepted
what does mean 0.0.0.0:22 under the column local address of netstat command?
0.0.0.0:22 in local address column means ssh daemon listen on all local ip.
So, if you have 2 IPs (say 192.168.0.10 and 90.87.65.123), your ssh daemon will listen on both IPs (and, of course on 127.0....
- 181
5
votes
Port 3000 is always being hogged by grafana-server
I have been struggling to figure this out for mac. This page kept showing up. So, to help other mac users please use the following command
brew services stop grafana
- 51
5
votes
Accepted
Which interface does a specific IP address will get routed over?
ip route get is what you're looking for; maybe it's ip route show to, depending on whether you checking should be allowed to change the routing state.
See man ip-route for more details.
- 51.5k
4
votes
What's the easiest way to find an unused local port?
If you have python lying around, I'd do this:
port="$(python -c 'import socket; s=socket.socket(); s.bind(("", 0)); print(s.getsockname()[1])')";
echo "Unused Port: $port"
4
votes
Netstat output line width limit
You can notice that the line width of the second output is short (ends at [). Is there any way so I get the proper output from netstat?
Unfortunately the width of the PID/Program name column in ...
- 173
4
votes
netstat output is "ESTABLISHED -" (no program name attached). What is the issue?
Since you are using root account, you can see all processes of all users so - indicates that connection is handled by kernel.
In order to handle connection you have to call listen() function with ...
- 2,023
4
votes
Is there documentation for /proc/net/netstat and /proc/net/snmp?
netstat -s has comments for each line
- 51
4
votes
Accepted
Process appear by "netstat" but doesn't appear by "ps -a"
A simple ps shows only your own processes, not system processes or other users' processes. ps allows options to show more processes, e.g. ps ax or ps -e or ps -A.
ps -a doesn't show the process ...
- 6,441
4
votes
How can I verify that the port forwarding is established by checking the sockets?
There are many complementary ways of doing it:
On your local machine
You can run your ssh command with -v option, and there will be information about forwarding:
debug1: Local connections to ...
- 2,146
4
votes
Accepted
Does `netstat` output different sockets with and without -n?
It's likely that one of the ports from the 720 list was simply removed in-between those runs; there should be no substantive difference in the number of outputs with or without -n.
You're seeing ...
- 68.8k
4
votes
Accepted
What do `0.0.0.0:*`, `[::]:mysql`, and `[::]:*` mean in netstat output?
0.0.0.0:* typically appears at the remote side of listening sockets, and indicates that remote address and port fields have not been filled in yet... which is logical for a socket that is listening ...
- 114k
4
votes
Accepted
Why does postgresql server have a `localhost:57504` to `localhost:57504` UDP "connection"?
A little bit of digging this is the stats collector. Apparently stats are posted on local loopback (aka localhost) UDP. See here: http://www.neilconway.org/talks/hacking/ottawa/ottawa_slides.pdf . ...
- 21k
4
votes
netstat cannot find opened port by iptables
There seems to be some confusion about what an 'open port' is. This is partly due to the informal way that everyone speaks about open ports.
With IP tables, you open a port for access (possibly with ...
- 5,063
4
votes
Accepted
Fresh Fedora 35 - what are these active internet connections doing?
The output is truncated, that was a connection to proxy14.fedoraproject.org, probably for an automated check for updates.
ss -rt
would show you the full host name.
- 481k
4
votes
Accepted
Show non-truncated usernames of users connected to sshd server in terminal?
ss does not print the username of the user connected to sshd as netstat does
netstat doesn't do that, either! It just prints the cmdline of that process. No guarantees that the user that's ...
- 51.5k
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