initial commit

server/server.go

@@ -0,0 +1,115 @@
+package server
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"log"
+	"net"
+)
+
+const (
+	MsgKeyPress  uint16 = 1
+	MsgGameState uint16 = 2
+)
+
+func Start() {
+	listener, err := net.Listen("tcp", ":9000")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println("Server listening on port 9000")
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			fmt.Println("Accept error:", err)
+			continue
+		}
+
+		fmt.Println("Client connected")
+
+		go handle(conn)
+	}
+}
+
+func SendPacket(conn net.Conn, msgID uint16, payload []byte) error {
+	// Length matches Lua: 2 (msgID) + payload size
+	length := uint32(2 + len(payload))
+	buf := make([]byte, 4+2+len(payload))
+
+	binary.BigEndian.PutUint32(buf[0:4], length)
+	binary.BigEndian.PutUint16(buf[4:6], msgID)
+	copy(buf[6:], payload)
+
+	n, err := conn.Write(buf)
+	if err != nil {
+		return err
+	}
+	if n != len(buf) {
+		return fmt.Errorf("short write: expected %d bytes, got %d", len(buf), n)
+	}
+	return nil
+}
+
+func handle(conn net.Conn) {
+	defer conn.Close()
+
+	for {
+		// Read packet length
+		var length uint32
+
+		err := binary.Read(conn, binary.BigEndian, &length)
+		if err != nil {
+			if err != io.EOF {
+				fmt.Println("Read length error:", err)
+			}
+
+			fmt.Println("Client disconnected")
+			return
+		}
+
+		// Prevent invalid packets
+		if length < 2 {
+			fmt.Println("Invalid packet length:", length)
+			return
+		}
+
+		// Read message ID
+		var msgID uint16
+
+		err = binary.Read(conn, binary.BigEndian, &msgID)
+		if err != nil {
+			fmt.Println("Read message ID error:", err)
+			return
+		}
+
+		// Read payload
+		payload := make([]byte, length-2)
+
+		_, err = io.ReadFull(conn, payload)
+		if err != nil {
+			fmt.Println("Read payload error:", err)
+			return
+		}
+
+		switch msgID {
+
+		case MsgKeyPress:
+			msg := string(payload)
+
+			fmt.Println(msg)
+
+			// Send something back to the client
+			err := SendPacket(conn, MsgGameState, []byte("received key press: "+msg))
+			if err != nil {
+				fmt.Println("Send error:", err)
+				return
+			}
+
+		default:
+			fmt.Println("Unknown message:", msgID)
+		}
+	}
+}