ESP32-S3 board
The brain — today it joins your network and listens.
01 First, know the pieces
What you need
Three things on the bench, plus one download for your computer — Processing, which arrives in the steps. Tap Define on anything unfamiliar; the answer opens as a field note you can read and dismiss without losing your place.
Arduino IDE
Uploads the sketch and opens Serial Monitor.
Official sketch
Sketch_24.2_WiFiServer.ino
02 One action at a time
Build it
All the wiring days led here — today the path is code, one download, and a conversation across your own network. Tap each step as you go to keep your place.
0 / 8 done
Open
Sketch_24.2_WiFiServer.inoin Arduino IDE.Replace the two
********placeholders with your own Wi-Fi name and password — the same network your computer is on.On your computer, install Processing from processing.org/download.
In Processing, add the ControlP5 library — Sketch → Import Library → Add Library, then search ControlP5.
Back in the sketch folder, open the bundled
sketchWiFi/sketchWiFi.pdein Processing and click Run.Upload the Arduino sketch, then open Serial Monitor at
115200and watch the board join your network and print its IP address and port 80.In sketchWiFi, choose TCP CLIENT mode, enter the board's printed IP and port
80, and connect.Type a line in sketchWiFi and press Enter — it lands in Serial Monitor. Answer from Serial Monitor's send box — it lands in sketchWiFi.
03 Read just enough code
Read the code
The sketch does two jobs. setup() joins your Wi-Fi as a station, prints the address the router assigned, and starts the server; loop() is a relay, carrying each line from the network to the monitor and each line from the monitor to the network. Switch to MicroPython to see the same idea in raw sockets.
#define port 80
WiFiServer server(port);
WiFi.begin(ssid_Router, password_Router);
server.begin(port);
WiFiClient client = server.accept(); // listen for incoming clients
Serial.println(client.readStringUntil('\n')); // print it out the serial monitor
client.print(Serial.readStringUntil('\n')); // print it out the client.WiFi.begin(ssid_Router, password_Router)Joins your router's network as a station — the router hands the board an IP address. server.begin(port)Starts listening at port 80 — a numbered door other machines can knock on. client.print(Serial.readStringUntil('\n'))Reads the line you typed in Serial Monitor and sends it down the network to the computer. Optional side path · no wiring
port = 8000 #input the remote port
listenSocket = socket.socket()
listenSocket.bind((ip,port))
listenSocket.listen(1)
print ('tcp waiting...')
conn,addr = listenSocket.accept()
print(addr,"connected")
conn.send('I am Server')listenSocket.bind((ip,port))Ties the listening socket to the board's own address and to port 8000.conn.send('I am Server')The first line down the wire the moment a client connects.Raw sockets this time, and port 8000 where the C sketch uses 80 — dial whichever port the running code printed. Run it in Thonny if MicroPython is set up; otherwise skip it — it should never block the Arduino-first day.
04 Understand, don't memorise
An address, a port, a service
Strip away the scale, and every connection on the internet is this same four-beat exchange. Today it happens entirely inside your own router.
Station mode
The board joins your Wi-Fi and the router hands it an address.
A door opens
server.begin() waits at port 80 — one numbered door at that address.
The client calls
Your computer knocks with the exact IP and port the monitor printed.
One shared line
Both ends read and write the same stream until one hangs up.
The model
server listens at an address and port → client dials it → one shared line
Day 29 gave it the address
Yesterday the board joined the network and the router handed it a number. Today it opens a door at that number and offers a service — an address, a port, and something listening.
What "on the internet" means
Every web server in the world is this same shape at larger scale — an address, a port, a service that answers when dialled. Your board now has all three.
05 Know it worked
Test & debug
Success and recovery sit side by side, so you never have to go hunting when something looks off.
What you should see
Connecting to YourNetworkName.....WiFi connected.IP address: 192.168.1.42IP port: 80Client connected.hello from the chart tableClient Disconnected.
Your address will differ — always dial the one your monitor just printed. The middle lines are whatever the two machines say to each other.
If it doesn't
- Dots forever? Re-check the Wi-Fi name and password in the sketch, confirm the network has a 2.4 GHz band, then press the board's reset button.
- Processing can't connect? Both machines must be on the same network — and use the IP the monitor just printed, since it changes between networks.
- ControlP5 error on Run? Install the library from Processing's Add Library window, then run the sketch again.
- Nothing arrives? Connect before typing, and end every line with Enter.
06 Make the idea yours
Try this: swap the roles
Same network, one last idea: the roles are a choice. It fits inside today's 30 minutes — and it closes the course.
Let the board dial out
Open Sketch_24.1_WiFiClient.ino, put your computer's address in REMOTE_IP, and run sketchWiFi in TCP SERVER mode on port 8888. The board dials in and introduces itself — "Hello", then "This is my IP."
Teach it a word
Back in the server sketch, check each incoming line and have the board client.print("aye\n") whenever the line contains "ahoy". A two-word protocol, and it's yours.
Logbook
07 Learn it with a hand on the tiller
Coach me through it
Every lesson ships with a code and a machine-readable packet, so an agent can guide you with full context.
Lesson code
TSK-DAY30-TCPIP
Context packet
How the agent should behave: guide one step at a time, wait for you to confirm, explain terms on request, and check credentials, the 2.4 GHz band, and the printed IP before changing code.