Port 80 of tomcat in Java was occupied

Met this port to be occupied problem today then all sorts of baidu say first

Use the last option of the command netstat -a-n-o to indicate the process id of the connection. Find the PID on port 8080 and open the task manager. Switch to the process TAB. Select the column, select PID. In the list to find the PID corresponding to the process can be found and then found that the process that occupies the port of PID is 4 but how to close can not close the process so baidu PID is 4 process found the same problem is the world wide web publishing service closed the service is fine. Pid 4 is a system reserved process but we don't know what that process is for but when you start it up again you're done with it and you've solved the problem