The netstat utility provides a command line interface to retrieve system routing tables, connection states, and network statistics. Two of the available statisticss, “tcpPassiveOpens” and “tcpActiveOpens,” provide data on the number of new connections to a server (tcpPassiveOpens), and the number of connections initiated by the server (tcpActiveOpens). Both statistics counters can be retrieved with netstat’s “-s” option, and a simple while loop allows a SysAdmin to get a high level view of TCP connections to and from a server:
while :
> do
> netstat -s | egrep '(tcpPassiveOpens|tcpActiveOpens)'
> sleep 10
> done
tcpActiveOpens = 6228 tcpPassiveOpens = 75
tcpActiveOpens = 6228 tcpPassiveOpens = 75
tcpActiveOpens = 6228 tcpPassiveOpens = 76
tcpActiveOpens = 6228 tcpPassiveOpens = 85
tcpActiveOpens = 6228 tcpPassiveOpens = 140
tcpActiveOpens = 6228 tcpPassiveOpens = 197
tcpActiveOpens = 6228 tcpPassiveOpens = 255
This is kinda fun to run on super busy web servers!!!