UDP is connectionless — send a packet, don't wait for acknowledgment.
Sending and Receiving
2 · Worked example — read every step
// Server: listen for packets
pc, err := net.ListenPacket("udp", ":5000")
if err != nil {
log.Fatal(err)
}
defer pc.Close()
buf := make([]byte, 1024)
for {
n, addr, err := pc.ReadFrom(buf)
if err != nil {
log.Println(err)
continue
}
msg := string(buf[:n])
slog.Info("received", "from", addr, "msg", msg)
pc.WriteTo([]byte("ACK: "+msg), addr) // respond to sender
}
// Client: send a packet
conn, err := net.Dial("udp", "localhost:5000")
if err != nil {
log.Fatal(err)
}
defer conn.Close()
conn.Write([]byte("hello"))
buf := make([]byte, 1024)
n, _ := conn.Read(buf)
fmt.Println(string(buf[:n])) // "ACK: hello"
When to Use UDP
| Use Case | Why UDP |
|---|---|
| DNS queries | Single request/response, low latency |
| Metrics (StatsD) | Losing a metric is fine, speed matters |
| Service discovery | Quick broadcast, no connection overhead |
| Game servers | Latency > reliability |
| Health pings | Simple, fast, stateless |
TCP guarantees delivery and ordering. UDP doesn't — but it's faster and simpler for fire-and-forget patterns.
3 · Fill the gaps
A UDP metrics listener, from memory — the packet API, not the stream API.
pc, err := net.("udp", ":9125")
if err != nil {
log.Fatal(err)
}
defer pc.Close()
buf := make([]byte, 1024)
for {
n, addr, err := pc.(buf)
if err != nil {
continue
}
metric := string()
pc.([]byte("ok: "+metric), addr)
}
4 · From scratch — this feeds your review queue