What is the Netstat Command?:
Specifically, the netstat command can show details about individual network connections, overall and protocol-specific networking statistics, and much more, all of which could help troubleshoot certain kinds of networking issues.
Netstat Command Syntax:
netstat [-a] [-b] [-e] [-f] [-n] [-o] [-p protocol] [-r] [-s] [-t] [-x] [-y] [time_interval] [/?]
Execute the netstat command alone to show a relatively simple list of all active TCP connections which, for each one, will show the local IP address (your computer), the foreign IP address (the other computer or network device), along with their respective port numbers, as well as the TCP state.
-a = This switch displays active TCP connections, TCP connections with the listening state, as well as UDP ports that are being listened to.
-b = This netstat switch is very similar to the -o switch listed below, but instead of displaying the PID, will display the process's actual file name. Using -b over -o might seem like it's saving you a step or two but using it can sometimes greatly extend the time it takes netstat to fully execute.
-e = Use this switch with the netstat command to show statistics about your network connection. This data includes bytes, unicast packets, non-unicast packets, discards, errors, and unknown protocols received and sent since the connection was established.
-f = The -f switch will force the netstat command to display the Fully Qualified Domain Name (FQDN) for each foreign IP addresses when possible.
-n = Use the -n switch to prevent netstat from attempting to determine host names for foreign IP addresses. Depending on your current network connections, using this switch could considerably reduce the time it takes for netstat to fully execute.
-o = A handy option for many troubleshooting tasks, the -o switch displays the process identifier (PID) associated with each displayed connection. See the example below for more about using netstat -o.
-p = Use the -p switch to show connections or statistics only for a particular protocol. You can not define more than one protocol at once, nor can you execute netstat with -p without defining a protocol.
protocol = When specifying a protocol with the -p option, you can use tcp, udp, tcpv6, or udpv6. If you use -s with -p to view statistics by protocol, you can use icmp, ip, icmpv6, or ipv6 in addition to the first four I mentioned.
-r = Execute netstat with -r to show the IP routing table. This is the same as using the route command to execute route print.
-s = The -s option can be used with the netstat command to show detailed statistics by protocol. You can limit the statistics shown to a particular protocol by using the -s option and specifying that protocol, but be sure to use -s before -p protocol when using the switches together.
-t = Use the -t switch to show the current TCP chimney offload state in place of the typically displayed TCP state.
-x = Use the -x option to show all NetworkDirect listeners, connections, and shared endpoints.
-y = The -y switch can be used to show the TCP connection template for all connection. You cannot use -y with any other netstat option.
time_interval = This is the time, in seconds, that you'd like the netstat command to re-execute automatically, stopping only when you use Ctrl-C to end the loop.
/? = Use the help switch to show details about the netstat command's several options.
Tip: Make all that netstat information in the command line easier to work with by outputting what you see on the screen to a text file using a redirection operator. See How To Redirect Command Output to a File for complete instructions.
Netstat Command Examples:
In this first example, I execute netstat to show all active TCP connections. However, I do want to see the computers I'm connected to in FQDN format [-f] instead of a simple IP address.
Here's an example of what you might see:
Active Connections Proto Local Address Foreign Address State TCP 127.0.0.1:5357 VM-Windows-7:49229 TIME_WAIT TCP 127.0.0.1:49225 VM-Windows-7:12080 TIME_WAIT TCP 192.168.1.14:49194 188.8.131.52:http CLOSE_WAIT TCP 192.168.1.14:49196 a795sm.avast.com:http CLOSE_WAIT TCP 192.168.1.14:49197 a795sm.avast.com:http CLOSE_WAIT TCP 192.168.1.14:49230 TIM-PC:wsd TIME_WAIT TCP 192.168.1.14:49231 TIM-PC:icslap ESTABLISHED TCP 192.168.1.14:49232 TIM-PC:netbios-ssn TIME_WAIT TCP 192.168.1.14:49233 TIM-PC:netbios-ssn TIME_WAIT TCP [::1]:2869 VM-Windows-7:49226 ESTABLISHED TCP [::1]:49226 VM-Windows-7:icslap ESTABLISHED
As you can see, I had 11 active TCP connections at the time I executed netstat. The only protocol (in the Proto column) listed is TCP, which was expected because I did not use -a.
You can also see three sets of IP addresses in the Local Address column - my actual IP address of 192.168.1.14 and both IPv4 and IPv6 versions of my loopback addresses, along with the port each connection is using. The Foreign Address column lists the FQDN (184.108.40.206 didn't resolve for some reason) along with that port as well.
Finally, the State column lists the TCP state of that particular connection.
In this example, I want to run netstat normally so it only shows active TCP connections, but I also want to see the corresponding process identifier [-o] for each connection so I can determine which program on my computer initiated each one.
Here's what my computer displayed:
Active Connections Proto Local Address Foreign Address State PID TCP 192.168.1.14:49194 220.127.116.11:http CLOSE_WAIT 2948 TCP 192.168.1.14:49196 a795sm:http CLOSE_WAIT 2948 TCP 192.168.1.14:49197 a795sm:http CLOSE_WAIT 2948
You probably noticed the new PID column. In this case, the PIDs are all the same, meaning that the same program on my computer opened these connections.
To determine what program is represented by the PID of 2948 on my computer, all I have to do is open Task Manager, click on the Processes tab, and note the Image Name listed next to the PID I'm looking for in the PID column.1
Using the netstat command with the -o option can be very helpful when tracking down which program is using too big a share of your bandwidth. It can also help locate the destination where some kind of malware, or even an otherwise legitimate piece of software, might be sending information without your permission.
Note: While this and the previous example were both run on the same computer, and within just a minute of each other, you can see that the list of active TCP connections is considerably different. This is because your computer is constantly connecting to, and disconnecting from, various other devices on your network and over the Internet.
netstat -s -p tcp -f
In this third example, I want to see protocol specific statistics [-s] but not all of them, just TCP stats [-p tcp]. I also want the foreign addresses displayed in FQDN format [-f].
This is what the netstat command, as shown above, produced on my computer:
TCP Statistics for IPv4 Active Opens = 77 Passive Opens = 21 Failed Connection Attempts = 2 Reset Connections = 25 Current Connections = 5 Segments Received = 7313 Segments Sent = 4824 Segments Retransmitted = 5 Active Connections Proto Local Address Foreign Address State TCP 127.0.0.1:2869 VM-Windows-7:49235 TIME_WAIT TCP 127.0.0.1:2869 VM-Windows-7:49238 ESTABLISHED TCP 127.0.0.1:49238 VM-Windows-7:icslap ESTABLISHED TCP 192.168.1.14:49194 18.104.22.168:http CLOSE_WAIT TCP 192.168.1.14:49196 a795sm.avast.com:http CLOSE_WAIT TCP 192.168.1.14:49197 a795sm.avast.com:http CLOSE_WAIT
As you can see, various statistics for the TCP protocol are displayed, as are all active TCP connections at the time.
netstat -e -t 5
In this final example, I executed the netstat command to show some basic network interface statistics [-e] and I wanted these statistics to continually update in the command window every five seconds [-t 5].
Here's what's produced on screen:
Interface Statistics Received Sent Bytes 22132338 1846834 Unicast packets 19113 9869 Non-unicast packets 0 0 Discards 0 0 Errors 0 0 Unknown protocols 0 Interface Statistics Received Sent Bytes 22134630 1846834 Unicast packets 19128 9869 Non-unicast packets 0 0 Discards 0 0 Errors 0 0 Unknown protocols 0 ^C
Various pieces of information, which you can see here and that I listed in the -e syntax above, are displayed.
I only let the netstat command automatically execute one extra time, as you can see by the two tables in the result. Note the ^C at the bottom, indicating that I used the Ctrl-C abort command to stop the rerunning of the command.
Netstat Command Availability:
The netstat command is available from within the Command Prompt in most versions of Windows including Windows 8, Windows 7, Windows Vista, Windows XP, Windows Server operating systems, and some older versions of Windows too.
Note: The availability of certain netstat command switches and other netstat command syntax may differ from operating system to operating system.
Netstat Related Commands:
 You may have to manually add the PID column to Task Manager. You can do this by selecting the "PID (Process Identifier)" checkbox from View -> Select Columns in Task Manager. You may also have to click the "Show processes from all users" button on the Processes tab if the PID you're looking for isn't listed.