Golang TinyMapleServer

main.go

package main

import (
	"bufio"
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"flag"
	"fmt"
	"net"
	"strconv"
)

var (
	version     int
	locale      int
	subversion  string
	port        int
	handshake   []byte
	appendedHex string
)

func handleConnection(con net.Conn) {
	buffer := make([]byte, 1024)

	writer := bufio.NewWriter(con)
	reader := bufio.NewReader(con)

	writer.Write(handshake)
	writer.Flush()

	// Keep reading
	for {
		if _, err := reader.Read(buffer); err != nil {
			fmt.Println("Client exited or something, idk.")
			return
		}
	}
}

func main() {
	flag.IntVar(&version, "version", 0, "MapleStory version")
	flag.StringVar(&subversion, "subversion", "", "MapleStory subversion")
	flag.IntVar(&locale, "locale", 0, "MapleStory locale")
	flag.StringVar(&appendedHex, "append-hex", "", "Additional bytes appended to the handshake (in HEX, without spaces)")
	flag.IntVar(&port, "port", 8484, "Port to listen on")

	flag.Parse()

	fmt.Println("Hosting tiny MapleStory server on port", port, "for version", version, ", subversion", subversion, "and locale", locale)

	buf := new(bytes.Buffer)

	handshakeSize := 2 + 2 + len(subversion) + 4 + 4 + 1

	binary.Write(buf, binary.LittleEndian, uint16(handshakeSize))
	binary.Write(buf, binary.LittleEndian, uint16(version))
	binary.Write(buf, binary.LittleEndian, uint16(len(subversion)))
	buf.Write([]byte(subversion))
	binary.Write(buf, binary.LittleEndian, uint32(0xBAADB00B))
	binary.Write(buf, binary.LittleEndian, uint32(0xDEADBEEF))
	binary.Write(buf, binary.LittleEndian, byte(locale))

	if hexBytes, err := hex.DecodeString(appendedHex); err != nil {
		panic(err)
	} else {
		buf.Write(hexBytes)
	}

	handshake = buf.Bytes()

	fmt.Println(hex.Dump(handshake))

	ln, err := net.Listen("tcp", ":"+strconv.Itoa(port))
	if err != nil {
		panic(err)
	}

	for {
		conn, err := ln.Accept()
		if err != nil {
			fmt.Println("Error while accepting client:", err)
		} else {
			fmt.Println("Got client!")
			go handleConnection(conn)
		}
	}
}