Networking Don't do this

3 TCP and UDP Mistakes That Cost Marks

3 mistakes that cost marks in TCP and UDP. Are you making one?

Lesson notes

Key points

Calling UDP connection-based: UDP sends datagrams with no setup or acknowledgement; only TCP is connection-oriented and reliable.
Handshake as SYN, ACK: The TCP handshake has three messages: SYN, then SYN-ACK, then ACK; never skip SYN-ACK.
Saying DNS uses only TCP: DNS queries normally use UDP port 53; TCP is used for large replies and zone transfers.

Takeaway: TCP: SYN, SYN-ACK, ACK. UDP: no handshake at all.

Quick check: What is the second message of the TCP three-way handshake?

ACK
SYN-ACK
FIN

The server replies to SYN with SYN-ACK, then the client sends ACK.

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