feat(server): UDP listener, hub WebSocket, Gauges Prometheus

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/transport/udp.go

@@ -0,0 +1,43 @@
+package transport
+
+import (
+	"encoding/json"
+	"log"
+	"net"
+
+	"github.com/user/nanometrics/server/models"
+)
+
+func StartUDP(addr string, handler func(*models.AgentMetrics)) error {
+	conn, err := net.ListenPacket("udp", addr)
+	if err != nil {
+		return err
+	}
+	log.Printf("[udp] écoute sur %s", addr)
+	go func() {
+		buf := make([]byte, 65535)
+		for {
+			n, _, err := conn.ReadFrom(buf)
+			if err != nil {
+				log.Printf("[udp] erreur lecture: %v", err)
+				continue
+			}
+			data := make([]byte, n)
+			copy(data, buf[:n])
+			go processUDP(data, handler)
+		}
+	}()
+	return nil
+}
+
+func processUDP(data []byte, handler func(*models.AgentMetrics)) {
+	var m models.AgentMetrics
+	if err := json.Unmarshal(data, &m); err != nil {
+		log.Printf("[udp] JSON invalide: %v", err)
+		return
+	}
+	if m.Hostname == "" {
+		return
+	}
+	handler(&m)
+}

server/transport/udp_test.go

@@ -0,0 +1,44 @@
+package transport_test
+
+import (
+	"encoding/json"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/user/nanometrics/server/models"
+	"github.com/user/nanometrics/server/transport"
+)
+
+func TestUDPReceive(t *testing.T) {
+	received := make(chan *models.AgentMetrics, 1)
+	err := transport.StartUDP("127.0.0.1:29999", func(m *models.AgentMetrics) {
+		received <- m
+	})
+	if err != nil {
+		t.Fatalf("start UDP: %v", err)
+	}
+
+	conn, err := net.Dial("udp", "127.0.0.1:29999")
+	if err != nil {
+		t.Fatalf("dial: %v", err)
+	}
+	defer conn.Close()
+
+	cpu := 55.0
+	m := models.AgentMetrics{Hostname: "test-01", IP: "127.0.0.1", Status: "online", CPUPercent: &cpu}
+	data, _ := json.Marshal(m)
+	conn.Write(data)
+
+	select {
+	case got := <-received:
+		if got.Hostname != "test-01" {
+			t.Errorf("hostname: attendu test-01, eu %s", got.Hostname)
+		}
+		if got.CPUPercent == nil || *got.CPUPercent != 55.0 {
+			t.Error("cpu_percent incorrect")
+		}
+	case <-time.After(time.Second):
+		t.Error("timeout: aucune métrique reçue")
+	}
+}