Networking Notes

TCP and UDP ports:

TCP checks for errors, and makes sure that the complete set of packets are sent successfully to the server. TCP ports can be used for web pages because the web page matters whether the complete information has been delivered.

UDP ports does not check for errors. It just keeps on sending packets. UDP ports can be used for live video streaming. If the UDP port will loose a packet while streaming, it just stops, and plays again for the next complete packets sent.

Linux Command Lines for Networking

• ping checks if there is a connection going to the target domain or ip address.
• ifconfig (Mac) or ipconfig (Windows) detects the ip address information on your computer.
• whois detects the domain owner and other information.
• tracert traces the connection from your router going to the target domain.
• dig shows the DNS setting of the target domain such as A record, cname, MX record.
• nslookup shows the IP address and the A record setting of the target domain
• hostname identifies the host where your computer is connected.
• tcpdump a command that allows you to see working packets in the terminal

Software for Networking

Wireshark can be used as a packet sniffer when used with tcpdump. To use it, try to connect your computer to the Internet with an ethernet cable. Then, wirelessly share your computer. Whoever will connect to your SSID (setup from your computer), their packets will pass through your computer. You must program Wireshark to see these packets moving. You may see the ip address packets are coming from and going to.

SSH

The SSH server allows you to connect SFTP to the server.

The SSH client can be any software program that connects to the remote computer with SSH.