computer networks

How does the internet(Web browser) work

DNS Protocol. Description and Packet Format

Router simulator and network utilities

Good and detailed material about OSI TCP/IP

Port information in windows

You can use netstat to list open ports and their state in Windows:

C:\WINDOWS>netstat -a -n

Active Connections

Proto Local Address Foreign Address State
TCP 0.0.0.0:1822 0.0.0.0:0 LISTENING
TCP 0.0.0.0:1837 0.0.0.0:0 LISTENING
TCP 0.0.0.0:2001 0.0.0.0:0 LISTENING
TCP 10.1.1.2:1026 0.0.0.0


Good tutorial on Arp