1, command mode

Let's take windows xp as an example to see which ports are opened in the newly installed system, that is, which doors are reserved. The command to view ports without using any tools is netstat, and the method is as follows:

A, type cmd at "Start" and "Run" and press Enter.

B in the dos command interface, type netstat -na to display the open service port, where proto

On behalf of the protocol, we can see that there are two protocols: tcp and udp. Local address stands for local address, and the number after the colon of this address is the open port number. A foreign address represents a remote address. If you are communicating with other machines, the address of the other party is displayed, and state stands for state. Listening displayed means that the port is open and waiting for a connection, but it is not connected yet. It's like your door has been opened, but no one has come in yet. Take the first behavior as an example to see what it means.

Tcp 0.0.0.0: 135 0.0.0.0:0 Listening.

This line indicates that the port 135 of this machine is waiting for a connection. Note: Only the service port of tcp protocol can be located in listening state.

Use the netstat command to view the port status.

2. use tcpview tool

In order to better analyze the port, it is best to use the software tcpview, which is very small, only 93kb, and it is a portable application and does not need to be installed.

The font was a little small when the display was first run. In options->; Just add a large font size to Font. The data displayed by tcpview is dynamic. In Figure 3, the local address shows which port is opened on this machine (the number after the symbol), and tcpview can see which port is started by which program. As can be seen from Figure 3, ports 445, 139, 1025, 135,5000 are open, ports 445, 139 are initiated by the system, and ports135 are initiated by svchost.