Assignment 6: Wi-Fi Server#
In this assignment, you’ll create an HTTP server running on your ESP32, serving web pages and controlling devices remotely.
Source Code Available: The HTTP server example is available in the developer-portal-codebase repository. See
content/workshops/tinygo/assignment_6/main.go for the complete working web server.HTTP Server with TinyGo#
TinyGo supports the standard net/http package on Wi-Fi-enabled boards, allowing you to create web servers easily.
What You’ll Build#
- HTTP server with multiple endpoints
- Serve static HTML pages
- Control LED via web interface
- Handle multiple concurrent clients
Board Support#
Wi-Fi is supported on:
- ESP32-C3: esp32c3-generic target
- ESP32-S3: esp32s3-generic target
NOT supported:
- ESP32 (original) - use ESP32-C3 or ESP32-S3 for Wi-Fi
Prerequisites#
Before using Wi-Fi examples, download required dependencies:
go mod download tinygo.org/x/espradio
go mod download tinygo.org/x/drivers
go mod download tinygo.org/x/espradio/netlink
Get the Source Code#
The complete source code for this assignment is available in the developer-portal-codebase repository:
git clone https://github.com/espressif/developer-portal-codebase.git
cd developer-portal-codebase/content/workshops/tinygo/assignment_6
The HTTP server example (main.go) includes:
- Web interface with LED control buttons
- JSON status endpoint
- Multiple route handlers
- ArenaPoolSize configuration for HTTP
Workshop credentials:
- SSID:
tinygo - Password:
gophercamp
Build and flash:
# ESP32-C3
tinygo flash -target esp32c3-generic \
-ldflags="-X main.ssid=tinygo -X main.password=gophercamp" \
main.go
See the README.md in the assignment directory for detailed instructions.
Basic HTTP Server#
Step 1: Create Project#
mkdir wifi-server
cd wifi-server
go mod init wifi-server
Workshop credentials for this session:
- SSID:
tinygo - Password:
gophercamp
Step 2: Create HTTP Server#
Create main.go:
package main
import (
"io"
"machine"
"net/http"
"time"
"tinygo.org/x/drivers/netdev"
nl "tinygo.org/x/drivers/netlink"
link "tinygo.org/x/espradio/netlink"
)
var ssid string
var password string
var ledPin = machine.GPIO10
func main() {
// Initialize LED
ledPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
// Initialize serial
serial := machine.Serial
serial.Configure(machine.UARTConfig{BaudRate: 115200})
serial.Write([]byte("HTTP Server\r\n"))
time.Sleep(2 * time.Second)
// Connect to Wi-Fi with larger arena pool for HTTP
radioLink := link.Esplink{
ArenaPoolSize: 48 * 1024, // Larger pool for HTTP connections
}
netdev.UseNetdev(&radioLink)
serial.Write([]byte("Connecting to Wi-Fi...\r\n"))
err := radioLink.NetConnect(&nl.ConnectParams{
Ssid: ssid,
Passphrase: password,
})
if err != nil {
serial.Write([]byte("Connection failed\r\n"))
return
}
serial.Write([]byte("Connected!\r\n"))
// Wait for DHCP
time.Sleep(5 * time.Second)
// Get IP address
addr, _ := radioLink.Addr()
host := addr.String()
serial.Write([]byte("Server: http://"))
serial.Write([]byte(host))
serial.Write([]byte(":8080\r\n"))
// Setup HTTP routes
http.Handle("/", logRequest(root))
http.Handle("/led/on", logRequest(ledOn))
http.Handle("/led/off", logRequest(ledOff))
http.Handle("/status", logRequest(status))
// Start server with explicit IP address
serial.Write([]byte("Starting server...\r\n"))
err = http.ListenAndServe(host+":8080", nil)
if err != nil {
serial.Write([]byte("Server error: "))
serial.Write([]byte(err.Error()))
serial.Write([]byte("\r\n"))
}
for {
time.Sleep(time.Second)
}
}
func logRequest(h http.HandlerFunc) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
serial := machine.Serial
serial.Write([]byte(r.Method))
serial.Write([]byte(" "))
serial.Write([]byte(r.URL.Path))
serial.Write([]byte("\r\n"))
h(w, r)
})
}
func root(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
io.WriteString(w, `<!DOCTYPE html>
<html>
<head>
<title>ESP32 TinyGo Server</title>
<style>
body { font-family: Arial; margin: 20px; }
h1 { color: #333; }
button { padding: 10px 20px; font-size: 16px; margin: 5px; }
.on { background: #4CAF50; color: white; }
.off { background: #f44336; color: white; }
</style>
</head>
<body>
<h1>ESP32 TinyGo Web Server</h1>
<p>Welcome to the TinyGo HTTP Server!</p>
<h2>LED Control</h2>
<button class="on" onclick="fetch('/led/on')">LED ON</button>
<button class="off" onclick="fetch('/led/off')">LED OFF</button>
<h2>Status</h2>
<button onclick="fetch('/status').then(r=>r.text()).then(d=>alert(d))">Check Status</button>
<h2>About</h2>
<p>This server is running on ESP32 with TinyGo 0.41</p>
<p>Board: ESP32-C3 / ESP32-S3</p>
</body>
</html>`)
}
func ledOn(w http.ResponseWriter, r *http.Request) {
ledPin.Low() // Active LOW
w.Header().Set("Content-Type", "text/plain")
io.WriteString(w, "LED ON")
}
func ledOff(w http.ResponseWriter, r *http.Request) {
ledPin.High() // Active LOW
w.Header().Set("Content-Type", "text/plain")
io.WriteString(w, "LED OFF")
}
func status(w http.ResponseWriter, r *http.Request) {
ledState := "OFF"
if ledPin.Get() {
ledState = "OFF" // Active LOW
} else {
ledState = "ON"
}
w.Header().Set("Content-Type", "application/json")
io.WriteString(w, `{"led":"`+ledState+`","uptime":"`+getUptime()+`"}`)
}
func getUptime() string {
return "unknown" // Simplified for example
}
Step 3: Build and Flash#
tinygo flash -target esp32c3-generic \
-ldflags="-X main.ssid=tinygo -X main.password=gophercamp" \
main.go
tinygo flash -target esp32s3-generic \
-ldflags="-X main.ssid=tinygo -X main.password=gophercamp" \
main.go
Step 4: Access Web Server#
- Watch serial output for IP address
- Open browser:
http://YOUR_BOARD_IP:8080(replace YOUR_BOARD_IP with actual IP) - Click buttons to control LED
- Check status
Troubleshooting#
Multiple Clients#
The net/http server handles multiple concurrent clients automatically:
// Server handles multiple requests concurrently
// Each request runs in its own goroutine
func data(w http.ResponseWriter, r *http.Request) {
// Simulate long operation
time.Sleep(time.Second * 2)
io.WriteString(w, "Data after 2 seconds")
}
Troubleshooting#
“Server not accessible”#
- Verify Wi-Fi connection is established
- Check firewall allows incoming connections
- Ensure browser uses correct IP and port (http://YOUR_BOARD_IP:8080)
- Try accessing from different device
“Connection refused”#
- Verify server is running
- Check port 8080 is not blocked
- Ensure IP address is correct
- Try restarting the board
“Server not accessible”#
- Verify Wi-Fi connection is established
- Check firewall allows incoming connections
- Ensure browser uses correct IP and port (http://YOUR_BOARD_IP:8080)
- Try accessing from different device
- Server binds to actual IP address, not wildcard
“Slow response”#
- Reduce sensor update rate
- Optimize HTML page size
- Check Wi-Fi signal strength
- Reduce concurrent requests
Security Considerations#
Security Notes:
- HTTP is not encrypted (use HTTPS for production)
- No authentication by default (add password protection)
- Open ports can be accessed by anyone on network
- Validate all user inputs
- Consider using API keys or tokens
Performance Tips#
- Keep responses small: Minimize HTML and JSON size
- Cache static content: Avoid regenerating same data
- Use appropriate timeouts: Don’t let connections hang
- Monitor memory: ESP32 has limited RAM
- Test concurrent load: Verify server handles multiple clients
Summary#
In this assignment, you learned:
- How to create an HTTP server on ESP32
- Serve static HTML pages
- Handle multiple routes and endpoints
- Control GPIO pins via web interface
- Display sensor data on web page
- Handle concurrent client requests
- Debug network issues
You can now create IoT devices with web interfaces!