Use netstat command in DOS to view the open ports in this machine. Netstat-a to see which ports are open netstat-n to see the network connection of ports netstat-v to see the work in progress netstat-ptcp/ip to see the usage of a protocol netstat-s to see the usage of all protocols in use. DOS is the abbreviation of English DiskOperatingSystem, which means "disk operating system". As the name implies, DOS is mainly a disk-oriented system software.