While connecting to any network, we might want to know the network activities going on in our PC for some reasons. For example, what is port being used by specific application? What are remote IP addresses currently accessed by the applications? How its network I/O status? Which connections are currently having LISTEN status? Etc.
There are ways to do that in Windows, one is using command line netstat. The other one is GUI based tool, called Resource Monitor.
Basically this command, as stated in Microsoft Technet Support, is to display TCP connection (with its related information, like IP, port, connection status, protocol). For connection status, 10 possible values are CLOSE_WAIT, CLOSED, ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, LAST_ACK, LISTEN, SYN_RECEIVED, SYN_SEND, TIMED_WAIT.
netstat [-a] [-e] [-n] [-o] [-p Protocol] [-r] [-s] [Interval]
-a : Displays all active TCP connections and the TCP and UDP ports on which the computer is listening.
-e : Displays Ethernet statistics, such as the number of bytes and packets sent and received. This parameter can be combined with -s.
-n : Displays active TCP connections, however, addresses and port numbers are expressed numerically and no attempt is made to determine names.
-o : Displays active TCP connections and includes the process ID (PID) for each connection. You can find the application based on the PID on the Processes tab in Windows Task Manager. This parameter can be combined with -a, -n, and -p.
-p Protocol : Shows connections for the protocol specified by Protocol. In this case, the Protocol can be tcp, udp, tcpv6, or udpv6. If this parameter is used with -s to display statistics by protocol, Protocol can be tcp, udp, icmp, ip, tcpv6, udpv6, icmpv6, or ipv6.
-s : Displays statistics by protocol. By default, statistics are shown for the TCP, UDP, ICMP, and IP protocols. If the IPv6 protocol for Windows XP is installed, statistics are shown for the TCP over IPv6, UDP over IPv6, ICMPv6, and IPv6 protocols. The -p parameter can be used to specify a set of protocols.
-r : Displays the contents of the IP routing table. This is equivalent to the route print command.
Interval : Redisplays the selected information every Interval seconds. Press CTRL+C to stop the redisplay. If this parameter is omitted, netstat prints the selected information only once.
/? : Displays help at the command prompt.
Below sample will show all TCP connections whose state “LISTENING”
netstat -a -p tcp | findstr LISTENING
This GUI based tool can be accessed on following ways: (1) Press Control+R, then type resmon, or (2) Search resmon in Start Program or (3) Open Task Manager – Click on Performance Tab, then Resource Monitor. While tool has been open, go to Network tab.
It has five main parts, Process with Network Activity, Network Activity, TCP connections, Listening ports, and Graph. Having more comprehensive while displaying the network activities, it will help network monitoring becoming easier.