Using Netstat To Check Ports Being Used


Netstat is a very useful command line tool used to display information on our application network activities such as ports on which the computer is listening, active TCP connections, IPv4 statistics, etc.

Syntax / Construction

netstat [-a] [-e] [-n] [-o] [-p Protocol] [-r] [-s] [Interval]


 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 tcpudptcpv6, or udpv6. If this parameter is used with -s to display statistics by protocol, Protocol can be tcpudpicmpiptcpv6udpv6icmpv6, 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.

Examples 1

Display all active TCP and UDP connections.

netstat -a

Result :

Examples 2

Display TCP only connections.

netstat -p tcp

Result :