netstat is a tool for viewing active network connections, listeners and sockets.

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136
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4answers
135k views

What's the difference between ip address 0.0.0.0 and 127.0.0.1?

I do know that 127.0.0.1 ~ 127.255.255.254 are the loopback IP addresses for most modern operating systems and we could use these IP addresses to refer to our own computer. But what's 0.0.0.0? It ...
24
votes
6answers
28k views

How to find other end of unix socket connection?

I have a process (dbus-daemon) which has many open connection over UNIX sockets. One of these connections is fd #36: =$ ps uw -p 23284 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME ...
19
votes
5answers
83k views

Huge amount of TIME_WAIT connections says netstat

Okay, this is creeping me out - I see about 1500-2500 of these: root@wherever:# netstat Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 ...
13
votes
8answers
41k views

How do I get rid of sockets in FIN_WAIT1 state?

I have a port that is blocked by a process I needed to kill. (a little telnet daemon that crashed). The process was killed successfully but the port is still in a 'FIN_WAIT1' state. It doesn't come ...
12
votes
4answers
48k views

How do I make cURL use keepalive from the command line?

I'm trying to verify that HTTP persistent connections are being used during communication with a Tomcat webserver I've got running. Currently, I can retrieve a resource on my server from a browser ...
11
votes
5answers
13k views

netstat shows a listening port with no pid but lsof does not

This question is similar to Network port open, but no process attached? I've tried everything from there, reviewed the logs, etc... and can't find anything. My netstat shows a TCP listening port and ...
10
votes
3answers
5k views

In the output for netstat what does the [::] mean?

In the results for netstat what does the [::] mean? example [::]:ssh [::]:* LISTEN
9
votes
4answers
4k views

TCP monitoring on a server: comparing netstat vs lsof?

I'm monitoring the TCP stack on a server hoping to generically infer problems with application on the box. My first inclination is to measure the number of sockets in all reported states ...
8
votes
3answers
2k views

Semantics of :: and 0.0.0.0 in dual-stack OSes

Back in the IPv4-only days, a LISTEN connection showing in netstat as listening on 0.0.0.0 would respond to connections on any IPv4 interface in the system. As I understand it, the new IPv6 idiom :: ...
8
votes
3answers
21k views

netstat -ntap doesn't show pid/process name for some connections?

I have ubuntu/hardy server, with kernel 2.6.24-23-server and netstat: # netstat --version net-tools 1.60 netstat 1.42 (2001-04-15) The problem is that we have a lot of ESTABLISHED connections that ...
7
votes
3answers
12k views

How to kill a TCP connection using tcpkill utility

I'm trying to kill an ESTABLISHED TCP connection using tcpkill. The connection is an open HTTPS connection. It appears on netstat as: tcp 0 0 X.X.X.X:55601 X.X.X.X:https ...
7
votes
3answers
7k views

TIME_WAIT connections not being cleaned up after timeout period expires

I am stress testing one of my servers by hitting it with a constant stream of new network connections, the tcp_fin_timeout is set to 60, so if I send a constant stream of something like 100 requests ...
7
votes
2answers
1k views

Where are my TIME_WAITs on Mac OS X?

No TIME_WAITs on Mac OS X Normally, when a TCP connection is closed, the socket on the side where close() is called first is left in the TIME_WAIT state. When one of the peers is a Mac OS X (Lion) ...
6
votes
4answers
17k views

Running lsof -i shows a lot of connections in CLOSE_WAIT ? Should I worry

So I am running lsof -i | wc -l periodically and it is telling me that out of 420 lines, between 240 and 255 are in CLOSE_WAIT state. How does TCP connections enter this state ? Should I be worried ...
6
votes
1answer
6k views

Port 80 being used by Microsoft-HTTPAPI/2.0

It's been quite a few days that port is being used by some strange process which i don't know Initially i thought it's related to SQL Server. I tried stopping all the services which starts from SQL ...
5
votes
5answers
10k views

Network port open, but no process attached?

I have a weird situation going on with an open network port. My main question is, why would there not be a program associated with an open TCP port: netstat -ln --program Active Internet connections ...
5
votes
1answer
2k views

Netstat hangs: why?

Sometimes (not too often at all) when I type "netstat", it takes over 5 seconds to return. While other times is instantaneous. I have been observing this for weeks on my server (CentOS 6.4), but I ...
5
votes
1answer
698 views

Why is rpc.lockd obscured from netstat/lsof output?

Prologue: On a number of machines, which happen to act as NFS clients, netstat reports two ports that are open with no PID listed for an associated daemon. Ordinarily this might be a bit concerning. ...
5
votes
3answers
2k views

How found suspect connection in a netstat output?

It seems some ssh brute force are outgoing from my debian 7.1. I'm searching how to find the source of these brute force. I'm searching in netstat output, but how can i identify trace of this hack ? ...
4
votes
8answers
31k views

Port 80 is being used by SYSTEM (PID 4), what is that?

I am trying to use port 80 for my application server, but when I perform "netstat -aon" I get TCP 0.0.0.0:80 0.0.0.0:0 LISTENING 4 When I look up the process in ...
4
votes
2answers
8k views

lots of packets pruned and packets collapsed because of socket buffer low/overrun

i've set up a test machine (debian squeeze 2.6.32 on a linode 2048 machine) that interact with an api that returns large chunks of json. It calls the API 3000/minutes asynchronously, the api is ...
4
votes
2answers
5k views

How to make netstat on Linux only show OUTBOUND tcp connections?

My ubuntu server is infected and there is a process making a bunch of HTTP requests to a bunch of websites (sucks!). I have added the following to my firewall (UFW): sudo ufw deny out proto tcp to ...
4
votes
2answers
1k views

How to know which process was using a port after it enters TIME_WAIT state?

On Linux, is there a way to figure out what process was using a port, before it went into TIME_WAIT state. When I use netstat -tnp I just see two end points, but no process information. Proto Recv-Q ...
4
votes
3answers
251 views

Windows Server 2008/2003 - determine all “used” local network ports

I have been tasked with enabling the local firewall on 100+ servers. The systems are running many different applications using many different ports. I began with an nmap scan, but without going to ...
3
votes
2answers
4k views

How to determine which TCP/UDP ports are being opened by a given process (linux)?

I know how to do the opposite (find out what process has a given port open) using lsof or netstat, but extensive research on Google hasn't helped me solve the reverse problem. I know I could use ...
3
votes
2answers
11k views

Netstat continuous refresh (watch changes the output)

I am using this simple command to monitor connections (to deal with some recent DOS attacks) on my Debian server: netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n How do I ...
3
votes
2answers
3k views

linux : netstat listeting queue length

Is there a way to view queue length on listening socket under linux, the same way as netstat -L outputs for freebsd? I.e. you can see X/Y/Z in netstat -L output, but netstat under linux doesn't ...
3
votes
2answers
386 views

After kill -9 process won't disappear and port is still bound

We have a Java server application running on Mac OS X. Occasionally this application has become unresponsive, and we have resorted to killing it with kill -9. However, the process doesn't disappear; ...
3
votes
1answer
346 views

AIX: is it somehow possible to get a ForeignAddress/PID pair like we are able to get in Linux with netstat?

In Linux (RHEL), we are able to get a ForeignAddress/PID pair with "netstat -ntp" command: [root@rhel ~]# netstat -ntp Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address ...
3
votes
1answer
667 views

Interpreting Netstat output

I have a LAMP stack running Fedora 12 and I am run the following instruction through the command line on the server: netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | ...
3
votes
1answer
656 views

What does it mean for netstat -t

I see the help of netstat -t option says Displays the current connection offload state. And I tried it in the windows command console. The Offload State value display InHost. What does Offload ...
3
votes
1answer
101 views

What is a good way to determine a server's connection usage?

Trying to figure out where my system's connections are being used (i.e. how many connections belong to what processes - could even be filtered by some expression through grep, if it applies). The ...
3
votes
2answers
4k views

netstat and ip_conntrack connection count differ by order of magnitude. Why?

in /proc/net/ip_conntrack I have: established 3076 time_wait 4346 total 7468 and in netstat I have: established 1051 time_wait 73 total 1165 Why is that? Where are other connections? How to ...
3
votes
2answers
2k views

What does each field of netstat -ano mean?

tcp 0 0 219.155.32.195:8888 221.137.227.51:5943 TIME_WAIT timewait (58.45/0/0) tcp 0 0 219.155.32.195:8888 221.137.227.51:5936 TIME_WAIT timewait ...
3
votes
3answers
920 views

python reports socket in use, netstat and others claim its not

We have a strange socket issue with a RHES3 box: Python 2.4.1 (#1, Jul 5 2005, 19:17:11) [GCC 3.2.3 20030502 (Red Hat Linux 3.2.3-52)] Type "help", "copyright", "credits" or "license" for more ...
3
votes
0answers
716 views

What does “connections reset due to unexpected data” in netstat -s mean

I'm running a memcached server under heavy load from multiple web servers. While investigating some odd app level behaviour, we spotted that netstat -s on the memcached box was showing a lot of ...
3
votes
2answers
3k views

UDP port appears to be in use but is not shown in netstat or TCPView

I've encountered some strange behavior I don't understand. I'm installing software on a Windows 2003 Server. This software needs to bind to a specific UDP port an all TCP addresses in order to listen ...
2
votes
2answers
170 views

How to map an ephemeral port to a pid?

I have a RHEL server with several apps on it and I am attempting to figure out which one of them is making calls to an external web service. I have TCP dumps that show the calls being made and through ...
2
votes
2answers
181 views

What does “::” denote in windows netstat results?

I'm trying to understand on which interfaces a TCP port is open Using windows netstat command I get result like : TCP [::]:10000 MyMachineName:0 LISTENING What does ...
2
votes
1answer
1k views

Netstat shows two sshd's listening, but only one pid

On my Linode sudo netstat -tulp gives me: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 *:ssh *:* LISTEN 2030/sshd ...
2
votes
2answers
187 views

Limit to number of listening ports in linux

I have tried to launch a script to listen to thousands of tcp ports (1000 to 10000) but it appears to be hitting a limit of 1024 listening ports. I've confirmed this via netstat and closed ports above ...
2
votes
2answers
424 views

When using netstat on a listening port what is the difference between localhost:6666 and [::]:6666 in 'Local Address' field

Using ubuntu 11.04, I run netstat -nplt the results for local address may be localhost:6666 or [::]:6666 What is the difference? I believe that the [::]: binds the service at ...
2
votes
2answers
5k views

analyse TCP performance by interpreting “netstat -s”

I have executed netstat -s on my dedicated server running debian. I'd like to interprete the results because I'm experiencing connectivity problems with TCP. I don't know how to read these results. ...
2
votes
1answer
218 views

Cannot Connect Via RDP

I cannot connect via RDP to a win2003 server. Terminal services say that they're started, but a netstat shows nothing to do with port 3389. Any ideas?
2
votes
1answer
8k views

Too many established connections left open

I have a (probably quite old) CentOS 4.5 server with a custom java application running inside. I found the application was crashing after some running time and found it was handling 1024 connections ...
2
votes
1answer
762 views

Can't Access CouchDB Remotely

Please keep in mind that I have this installed on an Amazon EC2 instance running the latest version of Ubuntu Server. I have changed the bind_address to 0.0.0.0. netstat -an | grep 5984 yields the ...
2
votes
2answers
1k views

iftop Shows Lots of Mysterious Connections - Not Showing in netstat

I've just stopped all pretty much all services except sshd on my server (Ubuntu Server 10.04), and when I run iftop I get output that looks like this: 12.5Kb 25.0Kb ...
2
votes
3answers
3k views

Unexplicated ssh connection from localhost through sshd to random localhost's port

I've tried to find out why I had some strange connections on my secure log file. Something like this : Apr 23 11:35:43 li192-61 sshd[11651]: Did not receive identification string from 127.0.0.1 Apr ...
2
votes
2answers
3k views

(node) Hit max file limit. Increase “ulimit -n”

In Ubuntu 9 I am receiving a message on my server that says: (node) Hit max file limit. Increase "ulimit -n" However, typing commands in the terminal reveals the following: $ ulimit ...
2
votes
1answer
10k views

Lots of TIME_WAIT connections in netstat (Windows Server 2008)

I'm having some issues on a Windows 2008 server with some network connections not going through. For instance, in a web application on the server, we need to open a socket connection to another ...