nginx
List and Count HTTP Connections
If you are investigating how many connections your HTTP server is getting probably if you suspect a Denial of Service attack or just plain interested, here is a simple command.
netstat -plant|grep :80|awk '{print $5}'|cut -d: -f1|sort|uniq -c|sort -n
It can be interchanged with any other services i.e. SMTP, just change :80 to :25.