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Programming Foundations
Phase 0Module 6 of 14

Networking

Your browser calls your API, your API calls OpenAI, agents call tools — all over the network. You need this to debug timeouts and secure services.

IP = street address, port = apartment number, DNS = phone book, firewall = security guard.

Visual Workflows

Start here — study each diagram, then use + / to zoom if needed.

Overview

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Key Takeaways

  • 1.Networking is how computers communicate — IP addresses, ports, DNS, and firewalls control every connection in your AI stack.
  • 2.TCP is reliable (HTTP, databases).
  • 3.DNS maps domain names to IPs.
  • 4.HTTPS adds TLS encryption.
  • 5.Security groups act as firewalls in the cloud.

Real Example

Scenario

Your agent can't connect to the vector database — connection times out every time.

What you would do

The DB is in a private subnet. Add a security group rule allowing port 5432 from the API subnet only.

Practice Task

Run ping google.com and nslookup google.com. Then run curl -v https://api.openai.com/v1/models (you will get 401 — that is expected; study the status code and headers in the output).

Commands

Commands to Remember

  • ping hostname # test if a host is reachable
  • nslookup hostname # resolve domain name to IP address
  • curl -v https://url # test an HTTP endpoint with full details
  • nc -zv host port # check if a specific port is open
  • traceroute hostname # trace the network path hop by hop

Cheat Sheet

Quick recap

quick ref
  • IP + port identifies every service on the network
  • DNS translates domain names to IP addresses
  • TCP = reliable · UDP = fast but may drop packets
  • HTTPS = HTTP encrypted with TLS
  • Common ports: 80 HTTP, 443 HTTPS, 5432 Postgres
  • Security groups / firewalls control allowed traffic

Common Mistakes

  • Exposing database ports to the internet
  • No timeouts on outbound HTTP calls
  • Ignoring latency when choosing cloud regions