I would recommend IPTABLES counter, you can show packet counter for each rule in iptables using
iptables -nL -v
the option -v here shows you the packet and byte count.
The only catch is you need to have a matching rule ( -j ACCEPT ) for each connection entry.
For example below rule counts all TCP packets generated from my linux box.
iptables -A OUTPUT -p tcp -j ACCEPT
Now I only need to run
iptables -nL -v
to see the bytes and packet count used.