add files

go.mod

@@ -0,0 +1,5 @@
+module server
+
+go 1.25.0
+
+require github.com/gorilla/websocket v1.5.3

go.sum

@@ -0,0 +1,2 @@
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=

main.go

@@ -0,0 +1,191 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"log"
+	"math/rand"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+const (
+	PacketHandshake uint8 = 0
+	PacketWorld     uint8 = 1
+
+	TickRate = 30
+	Speed    = 5.0
+
+	SpawnMinX   = -5.0
+	SpawnMaxX   = 5.0
+	SpawnMinZ   = -5.0
+	SpawnMaxZ   = 5.0
+	SpawnRadius = 1.5
+)
+
+type Player struct {
+	ID uint32
+
+	X float32
+	Y float32
+	Z float32
+
+	InputX float32
+	InputZ float32
+
+	Conn *websocket.Conn
+}
+
+var (
+	upgrader = websocket.Upgrader{
+		CheckOrigin: func(r *http.Request) bool { return true },
+	}
+
+	players   = make(map[uint32]*Player)
+	playersMu sync.Mutex
+	nextID    uint32 = 1
+)
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+
+	http.HandleFunc("/ws", handleWS)
+
+	go gameLoop()
+
+	log.Println("Server running on :8080")
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}
+
+func handleWS(w http.ResponseWriter, r *http.Request) {
+	conn, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		return
+	}
+
+	playersMu.Lock()
+	id := nextID
+	nextID++
+
+	x, z := randomSpawnPosition()
+
+	player := &Player{
+		ID:   id,
+		X:    x,
+		Y:    0,
+		Z:    z,
+		Conn: conn,
+	}
+	players[id] = player
+	playersMu.Unlock()
+
+	{
+		buf := new(bytes.Buffer)
+		binary.Write(buf, binary.LittleEndian, PacketHandshake)
+		binary.Write(buf, binary.LittleEndian, id)
+		conn.WriteMessage(websocket.BinaryMessage, buf.Bytes())
+	}
+
+	log.Println("Player connected:", id, "spawn at", x, z)
+
+	go readLoop(player)
+}
+
+func randomSpawnPosition() (float32, float32) {
+	for i := 0; i < 20; i++ {
+		x := rand.Float32()*(SpawnMaxX-SpawnMinX) + SpawnMinX
+		z := rand.Float32()*(SpawnMaxZ-SpawnMinZ) + SpawnMinZ
+
+		if isSpawnFree(x, z) {
+			return x, z
+		}
+	}
+
+	// fallback
+	return 0, 0
+}
+
+func isSpawnFree(x, z float32) bool {
+	for _, p := range players {
+		dx := p.X - x
+		dz := p.Z - z
+		if dx*dx+dz*dz < SpawnRadius*SpawnRadius {
+			return false
+		}
+	}
+	return true
+}
+
+func readLoop(p *Player) {
+	defer func() {
+		playersMu.Lock()
+		delete(players, p.ID)
+		playersMu.Unlock()
+
+		p.Conn.Close()
+		log.Println("Player disconnected:", p.ID)
+	}()
+
+	for {
+		_, data, err := p.Conn.ReadMessage()
+		if err != nil {
+			return
+		}
+
+		if len(data) < 8 {
+			continue
+		}
+
+		buf := bytes.NewReader(data)
+		binary.Read(buf, binary.LittleEndian, &p.InputX)
+		binary.Read(buf, binary.LittleEndian, &p.InputZ)
+	}
+}
+
+func gameLoop() {
+	ticker := time.NewTicker(time.Second / TickRate)
+	defer ticker.Stop()
+
+	dt := float32(1.0 / TickRate)
+
+	for range ticker.C {
+		update(dt)
+		broadcast()
+	}
+}
+
+func update(dt float32) {
+	playersMu.Lock()
+	defer playersMu.Unlock()
+
+	for _, p := range players {
+		p.X += p.InputX * Speed * dt
+		p.Z += p.InputZ * Speed * dt
+	}
+}
+
+func broadcast() {
+	playersMu.Lock()
+	defer playersMu.Unlock()
+
+	buf := new(bytes.Buffer)
+
+	binary.Write(buf, binary.LittleEndian, PacketWorld)
+	binary.Write(buf, binary.LittleEndian, uint16(len(players)))
+
+	for _, p := range players {
+		binary.Write(buf, binary.LittleEndian, p.ID)
+		binary.Write(buf, binary.LittleEndian, p.X)
+		binary.Write(buf, binary.LittleEndian, p.Y)
+		binary.Write(buf, binary.LittleEndian, p.Z)
+	}
+
+	data := buf.Bytes()
+
+	for _, p := range players {
+		p.Conn.WriteMessage(websocket.BinaryMessage, data)
+	}
+}