To find out the largest number of established connections you can simply use something like
netstat -an | grep 'ESTABLISHED' | awk '{print $4}' | cut -d: -f1 | uniq -c | sort -rn | head -n 1
To see the list of the top 10
netstat -an | grep 'ESTABLISHED' | awk '{print $4}' | cut -d: -f1 | uniq -c | sort -rn | head -n 10
To view all
netstat -an | grep 'ESTABLISHED' | awk '{print $4}' | cut -d: -f1 | uniq -c | sort -rn
You can also view all but have pages so you can view each in detail
netstat -an | grep 'ESTABLISHED' | awk '{print $4}' | cut -d: -f1 | uniq -c | sort -rn | more
You can show the port with
netstat -an | grep 'ESTABLISHED' | awk '{print $4}' | uniq -c | sort -rn |