CODEWITHSUNDEEP
linuxnetwork-programmingubuntu-12.04tcpdumpnetstat
RockyMountainHigh
RockyMountainHigh

Reputation: 3021

Getting count of open connections

I have automated the deployment of my application via fabric and have a new step that I need to add where I take my application out of rotation in the load balancer then, watch inbound connections from the balancer until they go to 0. Problem is, I am not sure how to get the count of inbound connections.

I can use tcpdump to watch my port POSTs. However, this is kind of hard to use in fabric. What I would like is to just run a loop with a timer that keeps getting the number of active inbound connections and exits on 0. Has anybody done anything like this? Or maybe someone would know how I might be able to achieve this from the shell and I can put it in fabric?

Upvotes: 1

Views: 4151

Answers (2)

nyxee
nyxee

Reputation: 2811

There might be a slight change somewhere but, this is what's working now.

netstat -an | awk '$1 == "tcp" && $4 ~ /:(80|443)$/' | wc -l
netstat -an | awk '$1 == "tcp" && $5 ~ /:(80|443)$/' | wc -l

From the current netstat help, -n means don't resolve names but -p only means display PID/Program name for sockets. So, the check on $4 and $5 in the awk in the above solution would fail.

Additionally, the above command also returns closed ports and other unestablished connections. So, we should use this instead:

netstat -an | awk '$1 == "tcp" && $4 ~ /:(80|443)$/ && $6==ESTABLISHED' | wc -l
netstat -an | awk '$1 == "tcp" && $5 ~ /:(80|443)$/ && $6==ESTABLISHED' | wc -l

Additionally, this also works::

netstat -ap | awk '$1 == "tcp" && $4 ~ /:(http|https)$/' | wc -l
netstat -ap | awk '$1 == "tcp" && $5 ~ /:(http|https)$/' | wc -l

Upvotes: 0

twalberg
twalberg

Reputation: 62369

netstat is one of the simplest ways to get this information, however, as you have noted, simply using grep to parse the output of netstat yields sub-optimal results, because it will match both incoming and outgoing connections (at least without a sufficiently complex search expression, or preprocessing with cut or the like). I would suggest this route, instead:

netstat -ap | awk '$1 == "tcp" && $4 ~ /:(80|443)$/' | wc -l

This will count connections that are TCP-based, and the local end is connected to either port 80 or 443, which would correspond with incoming connections. Replace $4 with $5 in that to catch outgoing connections instead.

Upvotes: 3

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