Netstat

NETSTAT [-a] [-e] [-n] [-s] [-p proto] [-r] [interval]

-a	Displays all connections and listening ports.
-e	Displays Ethernet statistics. This may be combined with the -s option.
-n	Displays addresses and port numbers in numerical form.
-p proto	Shows connections for the protocol specified by proto; proto may be TCP or UDP. If used with the -s option to display per-protocol statistics, proto may be TCP, UDP, or IP.
-r	Displays the routing table.
-s	Displays per-protocol statistics. By default, statistics are shown for TCP, UDP and IP; the -p option may be used to specify a subset of the default.

interval Redisplays selected statistics, pausing interval seconds
between each display. Press CTRL+C to stop redisplaying
statistics. If omitted, netstat will print the current
configuration information once.

C:\>netstat

Active Connections

Proto Local Address      Foreign Address                   State
TCP dummy:3174        www.microsoft.com:80         ESTABLISHED
TCP dummy:3175        www.microsoft.com:80         ESTABLISHED
TCP dummyt:3176        www.microsoft.com:80         ESTABLISHED
TCP dummy:3177         www.microsoft.com:80         ESTABLISHED
TCP dummy:3178        208.8.204.14:telnet               ESTABLISHED
TCP dummy:3181        chat.msn.com:6667               ESTABLISHED
TCP dummy:3182        hildrum.com:ftp                     ESTABLISHED
TCP dummy:3183        hildrum.com:ftp-data             ESTABLISHED

This is a simple example of just using netstat without any switches. As an example the following line:

TCP dummy:3181

chat.msn.com:6667

ESTABLISHED

shows that the computer with netbios name dummy (mine) is using port 3181 and is connected to chat.msn.com port 6667 using the TCP/IP protocol. As can be seen above I also have the webbrowser running connected to MS web site; a telent session going with 208.8.204.14 and an ftp session running with this place.

Here is an excellent atrticle from Cisco discussing NetBIOS-over-TCP/IP (NBT)

Cisco White Paper