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

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14
votes
5answers
63k 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 ...
9
votes
6answers
7k 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 ...
75
votes
4answers
79k 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 ...
4
votes
5answers
6k 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 ...
1
vote
3answers
2k views

Too Many ESTABLISHED connection from a single IP address in Apache

netstat -ntp |grep 80 shows too many ESTABLISHED connection from single IP address. Around 300 of them and it is not an attack and user is using a 2G connection to access Apache. This is the case ...
1
vote
4answers
2k views

Netstat: How to know if it's Human or Bot/Spider/DDOS

I'm using the following command to check how many connections I have from a single ip netstat -anp |grep ':80' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n If it's DDOS attack(500+ ...
17
votes
5answers
16k 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 ...
7
votes
3answers
6k 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 ...
2
votes
1answer
4k views

TIME_WAIT in netstat of Apache processes

What are the meaning of the TIME_WAIT when using netstat of my web server process? I am sure the web server is not over loaded. tcp 0 0 0.0.0.0:80 0.0.0.0:* ...
5
votes
1answer
574 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
4answers
12k 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 ...
1
vote
2answers
2k views

FreeBSD Listen Queue Overflows - can't increase max queue size

I have a decently high trafficked FreeBSD Nginx server, and I'm starting to get a large number of listen queue overflows: [root@svr ~]# netstat -sp tcp | fgrep listen 80361931 listen queue overflows ...
1
vote
3answers
718 views

Linux : restricting outgoing on an application basis

I typed : netstat -atlpvn and noticed that applications like gedit and python had foreign addresses outside the network (the network being a single computer connected to the internet). Is there ...