From 302388379ffcc6b870f5ace76660144b2c0c427a Mon Sep 17 00:00:00 2001
From: vaporvee <yannik@vaporvee.com>
Date: Wed, 17 Apr 2024 16:40:14 +0200
Subject: [PATCH] finalized basic udp server

---
 server/main.go | 113 ++++++++++++++++++++++++++++++++++---------------
 1 file changed, 79 insertions(+), 34 deletions(-)

diff --git a/server/main.go b/server/main.go
index 5567082..eb110ea 100644
--- a/server/main.go
+++ b/server/main.go
@@ -1,72 +1,117 @@
 package main
 
 import (
+	"crypto/rand"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
-	"net/http"
+	"io"
+	"net"
 	"os"
 
-	"github.com/gorilla/websocket"
 	"github.com/joho/godotenv"
 )
 
-var upgrader = websocket.Upgrader{
-	ReadBufferSize:  1024,
-	WriteBufferSize: 1024,
+type Payload struct {
+	Type      string `json:"type"`
+	Message   string `json:"msg,omitempty"`
+	Direction *struct {
+		X int `json:"x,omitempty"`
+		Y int `json:"y,omitempty"`
+	} `json:"direction,omitempty"`
+	SessionID string `json:"session_id,omitempty"`
 }
 
-var clients = make(map[*websocket.Conn]bool) // connected clients
-var broadcast = make(chan []byte)            // broadcast channel
+// Generate a unique session ID
+func generateSessionID() string {
+	b := make([]byte, 32)
+	if _, err := io.ReadFull(rand.Reader, b); err != nil {
+		return ""
+	}
+	return base64.URLEncoding.EncodeToString(b)
+}
 
 func main() {
 	godotenv.Load()
-	http.HandleFunc("/ws", handleConnections)
-	go handleMessages()
-	fmt.Println("Server running on " + os.Getenv("PORT"))
-	http.ListenAndServeTLS(os.Getenv("PORT"), "cert.pem", "key.pem", nil)
-}
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "4477" // Default port if not specified
+	}
 
-func handleConnections(w http.ResponseWriter, r *http.Request) {
-	conn, err := upgrader.Upgrade(w, r, nil)
+	addr, err := net.ResolveUDPAddr("udp", ":"+port)
 	if err != nil {
 		fmt.Println(err)
 		return
 	}
-	defer conn.Close() // Closes the connection at the end
 
-	clients[conn] = true // Add a new WebSocket connection to the clients map.
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	defer conn.Close()
+
+	fmt.Println("Server running on " + port)
+
+	buf := make([]byte, 1024)
+	clients := make(map[string]string) // Map to keep track of clients and their session IDs
 
 	for {
-		_, msg, err := conn.ReadMessage()
+		n, addr, err := conn.ReadFromUDP(buf)
 		if err != nil {
-			delete(clients, conn)
-			break
+			fmt.Println(err)
+			continue
 		}
 
-		// Parse the received message as JSON
-		var payload map[string]interface{}
-		err = json.Unmarshal(msg, &payload)
+		var payload Payload
+		err = json.Unmarshal(buf[:n], &payload)
 		if err != nil {
 			fmt.Println("Error parsing JSON:", err)
 			continue
 		}
 
-		// Check if the JSON object contains the key "type" with the value "broadcast"
-		if payload["type"] == "broadcast" {
-			broadcast <- msg // Send received WebSocket Message to Broadcast
+		// Use the client's IP and port as the key to uniquely identify the connection
+		key := addr.String()
+
+		// Check if the client's connection already has a session ID
+		if _, ok := clients[key]; !ok {
+			// The client is new, generate a session ID
+			sessionID := generateSessionID()
+			clients[key] = sessionID
+			// Send the session ID back to the client
+			responsePayload := Payload{SessionID: sessionID}
+			response, _ := json.Marshal(responsePayload)
+			conn.WriteToUDP(response, addr)
+		}
+
+		switch payload.Type {
+		case "init":
+			fmt.Printf("Received initiation generated SessionID: %s", clients[key])
+		case "move":
+			fmt.Printf("Received move message from Session ID: %s : X=%d, Y=%d\n", clients[key], payload.Direction.X, payload.Direction.Y)
+			// Handle movement logic here
+		case "message":
+			fmt.Printf("Received message from Session ID: %s : %s\n", clients[key], payload.Message)
+			broadcastMessage(conn, clients, payload.Message)
+		default:
+			fmt.Printf("Received unknown message type Session ID: %s\n", clients[key])
 		}
 	}
 }
 
-func handleMessages() {
-	for {
-		msg := <-broadcast
-		for client := range clients {
-			err := client.WriteMessage(websocket.TextMessage, msg)
-			if err != nil {
-				client.Close()
-				delete(clients, client)
-			}
+func broadcastMessage(conn *net.UDPConn, clients map[string]string, message string) {
+	for clientKey := range clients {
+		// Parse the clientKey to get the *net.UDPAddr
+		clientAddr, err := net.ResolveUDPAddr("udp", clientKey)
+		if err != nil {
+			fmt.Println("Error resolving UDP address:", err)
+			continue
 		}
+		payload := Payload{
+			Type:    "message",
+			Message: message,
+		}
+		response, _ := json.Marshal(payload)
+		conn.WriteToUDP(response, clientAddr)
 	}
 }