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I can't make lighttpd listen to port 80. 

~# /etc/init.d/lighttpd start
Starting web server: lighttpd2013-03-16 23:15:02: (network.c.379) can't bind to port:  80 Address already in use
 failed!

Actually I have apache2 installed on my server, too (listening to port 80) but it is not active.

I used netstat / netstat -npl but it wasn't helpful

How can I figure out what is using the port?

Lama
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4 Answers4

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In depsite of people got used to netstat for such kind of operations, it's good to know, that Linux has another great (and, actually superior) networking tool — ss. For e. g., to find out which process has opened port 80 you run it so:

sudo ss -pt state listening 'sport = :80'

so there's no need to pipe through external filters. Surely it has lots more useful knobs, so get yourself familiar with it.

For completeness sake and since recently I came across man fuser, I can also mention:

  • sudo fuser 80/tcp — this one also saves you from tinkering at cut/grep/awk… keep in mind this notation is a short-cut, in case there's an ambiguity, you should use one of namespaces allowed with -n …, like sudo fuser -n tcp 80

  • sudo lsof -n -sTCP:LISTEN -i:80 — was pointed out by @wallenborn. Meanwhile -n is not strictly required it's strongly advised since otherwise it uses DNS resolving which usualy slows down output terribly.

Community
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poige
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  • @Goot, if you mean binary, yep, at least `ls -l /proc/PID/exe` would do. And you mean its current work dir, see `…/cwd`. – poige Mar 16 '13 at 19:41
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Address already in use means that another process is already listening on port 80. Only one process can listen on a given port at a time.

To find the process, run as root:

netstat -tnlp | grep -w 80

The offending process will be listed.

Michael Hampton
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  • thanks, I figured out there is another instance of lighttpd running. I will accept your answer when it is possible. – Lama Mar 16 '13 at 19:33
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Another option with fewer keystrokes is lsof:

lsof -i :80
poige
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wallenborn
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  • Nope. It show not only listening processes. – poige Mar 18 '13 at 00:56
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    Correct use is a bit more longer: `lsof -n -sTCP:LISTEN -i:22` – poige Mar 18 '13 at 01:08
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    Correct use is a bit more longer: `sudo lsof -n -sTCP:LISTEN -i:80`. And it's better to use `sudo` explicitly to emphasize that unless user has superior permissions he might not be able to get correct results. – poige Mar 18 '13 at 01:14
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Old thread but who knows, someone has the same problem I had. In Apache2 I had more than one site enabled. In one of the site configurations (/etc/apache2/sites-available) the first line was 

listen 80

This caused a conflict with Apache itself! Because it was already listening on port 80 as a global config. Just remove the 'listen 80' from yoursite.conf if Apache has port 80 as a default port.

Pianoman
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