L3.3: Network Programming (1)

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L3.3 — Network Programming (Python) by Kirk Martinez. This lecture covers how to do network programming using Python's socket library — creating TCP and UDP sockets, the client-server echo pattern, address families (AF_INET vs AF_INET6), socket types (SOCK_STREAM vs SOCK_DGRAM), binding to interfaces/ports, DNS lookups with gethostbyname(), error handling for network code, the high-level HTTP requests library, WebSockets for persistent bidirectional connections (with asyncio), and Remote Procedure Calls (XML-RPC) for calling functions on remote machines.

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📋 At a Glance

[ ] Know what a socket is — the fundamental abstraction for sending/receiving data over a network
[ ] Know the address families: AF_INET (IPv4) and AF_INET6 (IPv6)
[ ] Know the socket types: SOCK_STREAM (TCP), SOCK_DGRAM (UDP), SOCK_RAW (ICMP etc.)
[ ] Know that socket.socket() with no arguments creates a default IPv4 TCP socket
[ ] Write a TCP echo server: socket → bind → listen → accept → recv/send loop
[ ] Write a TCP client: socket → connect → send → recv
[ ] Know that data must be sent as bytes (b'Hello'), not strings
[ ] Know that binding to '' (empty string) listens on all interfaces (Wi-Fi + Ethernet)
[ ] Use socket.gethostbyname() to resolve a hostname to an IP address via DNS
[ ] Write UDP client/server code using SOCK_DGRAM, sendto(), and recvfrom()
[ ] Know the difference: TCP needs connect/accept, UDP just sends/receives — no connection setup
[ ] Use try/except blocks to handle socket.error — especially important for UDP (expect packet loss)
[ ] Use the requests library for high-level HTTP: requests.get(), .post(), .put(), .delete()
[ ] Know that requests handles TCP, DNS, and even HTTPS (TLS) automatically
[ ] Explain what WebSockets are: persistent, bidirectional, low-latency channels (upgraded from HTTP)
[ ] Know WebSocket use cases: chat, games, IoT dashboards, financial data
[ ] Explain RPC (Remote Procedure Call): calling a function on a remote machine as if it were local