feat(protbot): add headless MHF protocol bot as cmd/protbot

Copy MHBridge into the Erupe module as cmd/protbot/ so it can be built, tested, and maintained alongside the server. The bot implements the full sign → entrance → channel login flow and supports lobby entry, chat, session setup, and quest enumeration. The conn/ package keeps its own Blowfish crypto primitives to avoid importing erupe-ce/config (which requires a config file at init).
2026-03-21 23:22:34 +01:00 · 2026-02-20 02:49:23 +01:00
parent 754b5a3bff
commit 0e84377e21
19 changed files with 2106 additions and 0 deletions
--- a/cmd/protbot/conn/bin8.go
+++ b/cmd/protbot/conn/bin8.go
@@ -0,0 +1,37 @@
+package conn
+
+import "encoding/binary"
+
+var (
+	bin8Key     = []byte{0x01, 0x23, 0x34, 0x45, 0x56, 0xAB, 0xCD, 0xEF}
+	sum32Table0 = []byte{0x35, 0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12}
+	sum32Table1 = []byte{0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12, 0xDE, 0xDE, 0x35}
+)
+
+// CalcSum32 calculates the custom MHF "sum32" checksum.
+func CalcSum32(data []byte) uint32 {
+	tableIdx0 := (len(data) + 1) & 0xFF
+	tableIdx1 := int((data[len(data)>>1] + 1) & 0xFF)
+	out := make([]byte, 4)
+	for i := 0; i < len(data); i++ {
+		key := data[i] ^ sum32Table0[(tableIdx0+i)%7] ^ sum32Table1[(tableIdx1+i)%9]
+		out[i&3] = (out[i&3] + key) & 0xFF
+	}
+	return binary.BigEndian.Uint32(out)
+}
+
+func rotate(k *uint32) {
+	*k = uint32(((54323 * uint(*k)) + 1) & 0xFFFFFFFF)
+}
+
+// DecryptBin8 decrypts MHF "binary8" data.
+func DecryptBin8(data []byte, key byte) []byte {
+	k := uint32(key)
+	output := make([]byte, len(data))
+	for i := 0; i < len(data); i++ {
+		rotate(&k)
+		tmp := data[i] ^ byte((k>>13)&0xFF)
+		output[i] = tmp ^ bin8Key[i&7]
+	}
+	return output
+}
--- a/cmd/protbot/conn/bin8_test.go
+++ b/cmd/protbot/conn/bin8_test.go
@@ -0,0 +1,52 @@
+package conn
+
+import (
+	"testing"
+)
+
+// TestCalcSum32 verifies the checksum against a known input.
+func TestCalcSum32(t *testing.T) {
+	// Verify determinism: same input gives same output.
+	data := []byte("Hello, MHF!")
+	sum1 := CalcSum32(data)
+	sum2 := CalcSum32(data)
+	if sum1 != sum2 {
+		t.Fatalf("CalcSum32 not deterministic: %08X != %08X", sum1, sum2)
+	}
+
+	// Different inputs produce different outputs (basic sanity).
+	data2 := []byte("Hello, MHF?")
+	sum3 := CalcSum32(data2)
+	if sum1 == sum3 {
+		t.Fatalf("CalcSum32 collision on different inputs: both %08X", sum1)
+	}
+}
+
+// TestDecryptBin8RoundTrip verifies that encrypting and decrypting with Bin8
+// produces the original data. We only have DecryptBin8, but we can verify
+// the encrypt→decrypt path by implementing encrypt inline here.
+func TestDecryptBin8RoundTrip(t *testing.T) {
+	original := []byte("Test data for Bin8 encryption round-trip")
+	key := byte(0x42)
+
+	// Encrypt (inline copy of Erupe's EncryptBin8)
+	k := uint32(key)
+	encrypted := make([]byte, len(original))
+	for i := 0; i < len(original); i++ {
+		rotate(&k)
+		tmp := bin8Key[i&7] ^ byte((k>>13)&0xFF)
+		encrypted[i] = original[i] ^ tmp
+	}
+
+	// Decrypt
+	decrypted := DecryptBin8(encrypted, key)
+
+	if len(decrypted) != len(original) {
+		t.Fatalf("length mismatch: got %d, want %d", len(decrypted), len(original))
+	}
+	for i := range original {
+		if decrypted[i] != original[i] {
+			t.Fatalf("byte %d: got 0x%02X, want 0x%02X", i, decrypted[i], original[i])
+		}
+	}
+}
--- a/cmd/protbot/conn/conn.go
+++ b/cmd/protbot/conn/conn.go
@@ -0,0 +1,52 @@
+package conn
+
+import (
+	"fmt"
+	"net"
+)
+
+// MHFConn wraps a CryptConn and provides convenience methods for MHF connections.
+type MHFConn struct {
+	*CryptConn
+	RawConn net.Conn
+}
+
+// DialWithInit connects to addr and sends the 8 NULL byte initialization
+// required by sign and entrance servers.
+func DialWithInit(addr string) (*MHFConn, error) {
+	conn, err := net.Dial("tcp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("dial %s: %w", addr, err)
+	}
+
+	// Sign and entrance servers expect 8 NULL bytes to initialize the connection.
+	_, err = conn.Write(make([]byte, 8))
+	if err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("write init bytes to %s: %w", addr, err)
+	}
+
+	return &MHFConn{
+		CryptConn: NewCryptConn(conn),
+		RawConn:   conn,
+	}, nil
+}
+
+// DialDirect connects to addr without sending initialization bytes.
+// Used for channel server connections.
+func DialDirect(addr string) (*MHFConn, error) {
+	conn, err := net.Dial("tcp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("dial %s: %w", addr, err)
+	}
+
+	return &MHFConn{
+		CryptConn: NewCryptConn(conn),
+		RawConn:   conn,
+	}, nil
+}
+
+// Close closes the underlying connection.
+func (c *MHFConn) Close() error {
+	return c.RawConn.Close()
+}
--- a/cmd/protbot/conn/crypt_conn.go
+++ b/cmd/protbot/conn/crypt_conn.go
@@ -0,0 +1,115 @@
+package conn
+
+import (
+	"encoding/hex"
+	"errors"
+	"erupe-ce/network/crypto"
+	"fmt"
+	"io"
+	"net"
+)
+
+// CryptConn is an MHF encrypted two-way connection.
+// Adapted from Erupe's network/crypt_conn.go with config dependency removed.
+// Hardcoded to ZZ mode (supports Pf0-based extended data size).
+type CryptConn struct {
+	conn                        net.Conn
+	readKeyRot                  uint32
+	sendKeyRot                  uint32
+	sentPackets                 int32
+	prevRecvPacketCombinedCheck uint16
+	prevSendPacketCombinedCheck uint16
+}
+
+// NewCryptConn creates a new CryptConn with proper default values.
+func NewCryptConn(conn net.Conn) *CryptConn {
+	return &CryptConn{
+		conn:       conn,
+		readKeyRot: 995117,
+		sendKeyRot: 995117,
+	}
+}
+
+// ReadPacket reads a packet from the connection and returns the decrypted data.
+func (cc *CryptConn) ReadPacket() ([]byte, error) {
+	headerData := make([]byte, CryptPacketHeaderLength)
+	_, err := io.ReadFull(cc.conn, headerData)
+	if err != nil {
+		return nil, err
+	}
+
+	cph, err := NewCryptPacketHeader(headerData)
+	if err != nil {
+		return nil, err
+	}
+
+	// ZZ mode: extended data size using Pf0 field.
+	encryptedPacketBody := make([]byte, uint32(cph.DataSize)+(uint32(cph.Pf0-0x03)*0x1000))
+	_, err = io.ReadFull(cc.conn, encryptedPacketBody)
+	if err != nil {
+		return nil, err
+	}
+
+	if cph.KeyRotDelta != 0 {
+		cc.readKeyRot = uint32(cph.KeyRotDelta) * (cc.readKeyRot + 1)
+	}
+
+	out, combinedCheck, check0, check1, check2 := crypto.Crypto(encryptedPacketBody, cc.readKeyRot, false, nil)
+	if cph.Check0 != check0 || cph.Check1 != check1 || cph.Check2 != check2 {
+		fmt.Printf("got c0 %X, c1 %X, c2 %X\n", check0, check1, check2)
+		fmt.Printf("want c0 %X, c1 %X, c2 %X\n", cph.Check0, cph.Check1, cph.Check2)
+		fmt.Printf("headerData:\n%s\n", hex.Dump(headerData))
+		fmt.Printf("encryptedPacketBody:\n%s\n", hex.Dump(encryptedPacketBody))
+
+		// Attempt bruteforce recovery.
+		fmt.Println("Crypto out of sync? Attempting bruteforce")
+		for key := byte(0); key < 255; key++ {
+			out, combinedCheck, check0, check1, check2 = crypto.Crypto(encryptedPacketBody, 0, false, &key)
+			if cph.Check0 == check0 && cph.Check1 == check1 && cph.Check2 == check2 {
+				fmt.Printf("Bruteforce successful, override key: 0x%X\n", key)
+				cc.prevRecvPacketCombinedCheck = combinedCheck
+				return out, nil
+			}
+		}
+
+		return nil, errors.New("decrypted data checksum doesn't match header")
+	}
+
+	cc.prevRecvPacketCombinedCheck = combinedCheck
+	return out, nil
+}
+
+// SendPacket encrypts and sends a packet.
+func (cc *CryptConn) SendPacket(data []byte) error {
+	keyRotDelta := byte(3)
+
+	if keyRotDelta != 0 {
+		cc.sendKeyRot = uint32(keyRotDelta) * (cc.sendKeyRot + 1)
+	}
+
+	encData, combinedCheck, check0, check1, check2 := crypto.Crypto(data, cc.sendKeyRot, true, nil)
+
+	header := &CryptPacketHeader{}
+	header.Pf0 = byte(((uint(len(encData)) >> 12) & 0xF3) | 3)
+	header.KeyRotDelta = keyRotDelta
+	header.PacketNum = uint16(cc.sentPackets)
+	header.DataSize = uint16(len(encData))
+	header.PrevPacketCombinedCheck = cc.prevSendPacketCombinedCheck
+	header.Check0 = check0
+	header.Check1 = check1
+	header.Check2 = check2
+
+	headerBytes, err := header.Encode()
+	if err != nil {
+		return err
+	}
+
+	_, err = cc.conn.Write(append(headerBytes, encData...))
+	if err != nil {
+		return err
+	}
+	cc.sentPackets++
+	cc.prevSendPacketCombinedCheck = combinedCheck
+
+	return nil
+}
--- a/cmd/protbot/conn/crypt_conn_test.go
+++ b/cmd/protbot/conn/crypt_conn_test.go
@@ -0,0 +1,152 @@
+package conn
+
+import (
+	"io"
+	"net"
+	"testing"
+)
+
+// TestCryptConnRoundTrip verifies that encrypting and decrypting a packet
+// through a pair of CryptConn instances produces the original data.
+func TestCryptConnRoundTrip(t *testing.T) {
+	// Create an in-process TCP pipe.
+	server, client := net.Pipe()
+	defer server.Close()
+	defer client.Close()
+
+	sender := NewCryptConn(client)
+	receiver := NewCryptConn(server)
+
+	testCases := [][]byte{
+		{0x00, 0x14, 0x00, 0x00, 0x00, 0x01}, // Minimal login-like packet
+		{0xDE, 0xAD, 0xBE, 0xEF},
+		make([]byte, 256), // Larger packet
+	}
+
+	for i, original := range testCases {
+		// Send in a goroutine to avoid blocking.
+		errCh := make(chan error, 1)
+		go func() {
+			errCh <- sender.SendPacket(original)
+		}()
+
+		received, err := receiver.ReadPacket()
+		if err != nil {
+			t.Fatalf("case %d: ReadPacket error: %v", i, err)
+		}
+
+		if err := <-errCh; err != nil {
+			t.Fatalf("case %d: SendPacket error: %v", i, err)
+		}
+
+		if len(received) != len(original) {
+			t.Fatalf("case %d: length mismatch: got %d, want %d", i, len(received), len(original))
+		}
+		for j := range original {
+			if received[j] != original[j] {
+				t.Fatalf("case %d: byte %d mismatch: got 0x%02X, want 0x%02X", i, j, received[j], original[j])
+			}
+		}
+	}
+}
+
+// TestCryptPacketHeaderRoundTrip verifies header encode/decode.
+func TestCryptPacketHeaderRoundTrip(t *testing.T) {
+	original := &CryptPacketHeader{
+		Pf0:                     0x03,
+		KeyRotDelta:             0x03,
+		PacketNum:               42,
+		DataSize:                100,
+		PrevPacketCombinedCheck: 0x1234,
+		Check0:                 0xAAAA,
+		Check1:                 0xBBBB,
+		Check2:                 0xCCCC,
+	}
+
+	encoded, err := original.Encode()
+	if err != nil {
+		t.Fatalf("Encode error: %v", err)
+	}
+
+	if len(encoded) != CryptPacketHeaderLength {
+		t.Fatalf("encoded length: got %d, want %d", len(encoded), CryptPacketHeaderLength)
+	}
+
+	decoded, err := NewCryptPacketHeader(encoded)
+	if err != nil {
+		t.Fatalf("NewCryptPacketHeader error: %v", err)
+	}
+
+	if *decoded != *original {
+		t.Fatalf("header mismatch:\ngot  %+v\nwant %+v", *decoded, *original)
+	}
+}
+
+// TestMultiPacketSequence verifies that key rotation stays in sync across
+// multiple sequential packets.
+func TestMultiPacketSequence(t *testing.T) {
+	server, client := net.Pipe()
+	defer server.Close()
+	defer client.Close()
+
+	sender := NewCryptConn(client)
+	receiver := NewCryptConn(server)
+
+	for i := 0; i < 10; i++ {
+		data := []byte{byte(i), byte(i + 1), byte(i + 2), byte(i + 3)}
+
+		errCh := make(chan error, 1)
+		go func() {
+			errCh <- sender.SendPacket(data)
+		}()
+
+		received, err := receiver.ReadPacket()
+		if err != nil {
+			t.Fatalf("packet %d: ReadPacket error: %v", i, err)
+		}
+
+		if err := <-errCh; err != nil {
+			t.Fatalf("packet %d: SendPacket error: %v", i, err)
+		}
+
+		for j := range data {
+			if received[j] != data[j] {
+				t.Fatalf("packet %d byte %d: got 0x%02X, want 0x%02X", i, j, received[j], data[j])
+			}
+		}
+	}
+}
+
+// TestDialWithInit verifies that DialWithInit sends 8 NULL bytes on connect.
+func TestDialWithInit(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+
+	done := make(chan []byte, 1)
+	go func() {
+		conn, err := listener.Accept()
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+		buf := make([]byte, 8)
+		_, _ = io.ReadFull(conn, buf)
+		done <- buf
+	}()
+
+	c, err := DialWithInit(listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	initBytes := <-done
+	for i, b := range initBytes {
+		if b != 0 {
+			t.Fatalf("init byte %d: got 0x%02X, want 0x00", i, b)
+		}
+	}
+}
--- a/cmd/protbot/conn/crypt_packet.go
+++ b/cmd/protbot/conn/crypt_packet.go
@@ -0,0 +1,78 @@
+// Package conn provides MHF encrypted connection primitives.
+//
+// This is adapted from Erupe's network/crypt_packet.go to avoid importing
+// erupe-ce/config (whose init() calls os.Exit without a config file).
+package conn
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+const CryptPacketHeaderLength = 14
+
+// CryptPacketHeader represents the parsed information of an encrypted packet header.
+type CryptPacketHeader struct {
+	Pf0                     byte
+	KeyRotDelta             byte
+	PacketNum               uint16
+	DataSize                uint16
+	PrevPacketCombinedCheck uint16
+	Check0                  uint16
+	Check1                  uint16
+	Check2                  uint16
+}
+
+// NewCryptPacketHeader parses raw bytes into a CryptPacketHeader.
+func NewCryptPacketHeader(data []byte) (*CryptPacketHeader, error) {
+	var c CryptPacketHeader
+	r := bytes.NewReader(data)
+
+	if err := binary.Read(r, binary.BigEndian, &c.Pf0); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.KeyRotDelta); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.PacketNum); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.DataSize); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.PrevPacketCombinedCheck); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.Check0); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.Check1); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(r, binary.BigEndian, &c.Check2); err != nil {
+		return nil, err
+	}
+
+	return &c, nil
+}
+
+// Encode encodes the CryptPacketHeader into raw bytes.
+func (c *CryptPacketHeader) Encode() ([]byte, error) {
+	buf := bytes.NewBuffer([]byte{})
+	data := []interface{}{
+		c.Pf0,
+		c.KeyRotDelta,
+		c.PacketNum,
+		c.DataSize,
+		c.PrevPacketCombinedCheck,
+		c.Check0,
+		c.Check1,
+		c.Check2,
+	}
+	for _, v := range data {
+		if err := binary.Write(buf, binary.BigEndian, v); err != nil {
+			return nil, err
+		}
+	}
+	return buf.Bytes(), nil
+}
--- a/cmd/protbot/main.go
+++ b/cmd/protbot/main.go
@@ -0,0 +1,154 @@
+// protbot is a headless MHF protocol bot for testing Erupe server instances.
+//
+// Usage:
+//
+//	protbot --sign-addr 127.0.0.1:53312 --user test --pass test --action login
+//	protbot --sign-addr 127.0.0.1:53312 --user test --pass test --action lobby
+//	protbot --sign-addr 127.0.0.1:53312 --user test --pass test --action session
+//	protbot --sign-addr 127.0.0.1:53312 --user test --pass test --action chat --message "Hello"
+//	protbot --sign-addr 127.0.0.1:53312 --user test --pass test --action quests
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"erupe-ce/cmd/protbot/scenario"
+)
+
+func main() {
+	signAddr := flag.String("sign-addr", "127.0.0.1:53312", "Sign server address (host:port)")
+	user := flag.String("user", "", "Username")
+	pass := flag.String("pass", "", "Password")
+	action := flag.String("action", "login", "Action to perform: login, lobby, session, chat, quests")
+	message := flag.String("message", "", "Chat message to send (used with --action chat)")
+	flag.Parse()
+
+	if *user == "" || *pass == "" {
+		fmt.Fprintln(os.Stderr, "error: --user and --pass are required")
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	switch *action {
+	case "login":
+		result, err := scenario.Login(*signAddr, *user, *pass)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "login failed: %v\n", err)
+			os.Exit(1)
+		}
+		fmt.Println("[done] Login successful!")
+		result.Channel.Close()
+
+	case "lobby":
+		result, err := scenario.Login(*signAddr, *user, *pass)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "login failed: %v\n", err)
+			os.Exit(1)
+		}
+		if err := scenario.EnterLobby(result.Channel); err != nil {
+			fmt.Fprintf(os.Stderr, "enter lobby failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+		fmt.Println("[done] Lobby entry successful!")
+		result.Channel.Close()
+
+	case "session":
+		result, err := scenario.Login(*signAddr, *user, *pass)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "login failed: %v\n", err)
+			os.Exit(1)
+		}
+		charID := result.Sign.CharIDs[0]
+		if _, err := scenario.SetupSession(result.Channel, charID); err != nil {
+			fmt.Fprintf(os.Stderr, "session setup failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+		if err := scenario.EnterLobby(result.Channel); err != nil {
+			fmt.Fprintf(os.Stderr, "enter lobby failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+		fmt.Println("[session] Connected. Press Ctrl+C to disconnect.")
+		waitForSignal()
+		scenario.Logout(result.Channel)
+
+	case "chat":
+		result, err := scenario.Login(*signAddr, *user, *pass)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "login failed: %v\n", err)
+			os.Exit(1)
+		}
+		charID := result.Sign.CharIDs[0]
+		if _, err := scenario.SetupSession(result.Channel, charID); err != nil {
+			fmt.Fprintf(os.Stderr, "session setup failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+		if err := scenario.EnterLobby(result.Channel); err != nil {
+			fmt.Fprintf(os.Stderr, "enter lobby failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+
+		// Register chat listener.
+		scenario.ListenChat(result.Channel, func(msg scenario.ChatMessage) {
+			fmt.Printf("[chat] <%s> (type=%d): %s\n", msg.SenderName, msg.ChatType, msg.Message)
+		})
+
+		// Send a message if provided.
+		if *message != "" {
+			if err := scenario.SendChat(result.Channel, 0x03, 1, *message, *user); err != nil {
+				fmt.Fprintf(os.Stderr, "send chat failed: %v\n", err)
+			}
+		}
+
+		fmt.Println("[chat] Listening for chat messages. Press Ctrl+C to disconnect.")
+		waitForSignal()
+		scenario.Logout(result.Channel)
+
+	case "quests":
+		result, err := scenario.Login(*signAddr, *user, *pass)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "login failed: %v\n", err)
+			os.Exit(1)
+		}
+		charID := result.Sign.CharIDs[0]
+		if _, err := scenario.SetupSession(result.Channel, charID); err != nil {
+			fmt.Fprintf(os.Stderr, "session setup failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+		if err := scenario.EnterLobby(result.Channel); err != nil {
+			fmt.Fprintf(os.Stderr, "enter lobby failed: %v\n", err)
+			result.Channel.Close()
+			os.Exit(1)
+		}
+
+		data, err := scenario.EnumerateQuests(result.Channel, 0, 0)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "enumerate quests failed: %v\n", err)
+			scenario.Logout(result.Channel)
+			os.Exit(1)
+		}
+		fmt.Printf("[quests] Received %d bytes of quest data\n", len(data))
+		scenario.Logout(result.Channel)
+
+	default:
+		fmt.Fprintf(os.Stderr, "unknown action: %s (supported: login, lobby, session, chat, quests)\n", *action)
+		os.Exit(1)
+	}
+}
+
+// waitForSignal blocks until SIGINT or SIGTERM is received.
+func waitForSignal() {
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	<-sig
+	fmt.Println("\n[signal] Shutting down...")
+}
--- a/cmd/protbot/protocol/channel.go
+++ b/cmd/protbot/protocol/channel.go
@@ -0,0 +1,190 @@
+package protocol
+
+import (
+	"encoding/binary"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"erupe-ce/cmd/protbot/conn"
+)
+
+// PacketHandler is a callback invoked when a server-pushed packet is received.
+type PacketHandler func(opcode uint16, data []byte)
+
+// ChannelConn manages a connection to a channel server.
+type ChannelConn struct {
+	conn       *conn.MHFConn
+	ackCounter uint32
+	waiters    sync.Map // map[uint32]chan *AckResponse
+	handlers   sync.Map // map[uint16]PacketHandler
+	closed     atomic.Bool
+}
+
+// OnPacket registers a handler for a specific server-pushed opcode.
+// Only one handler per opcode; later registrations replace earlier ones.
+func (ch *ChannelConn) OnPacket(opcode uint16, handler PacketHandler) {
+	ch.handlers.Store(opcode, handler)
+}
+
+// AckResponse holds the parsed ACK data from the server.
+type AckResponse struct {
+	AckHandle        uint32
+	IsBufferResponse bool
+	ErrorCode        uint8
+	Data             []byte
+}
+
+// ConnectChannel establishes a connection to a channel server.
+// Channel servers do NOT use the 8 NULL byte initialization.
+func ConnectChannel(addr string) (*ChannelConn, error) {
+	c, err := conn.DialDirect(addr)
+	if err != nil {
+		return nil, fmt.Errorf("channel connect: %w", err)
+	}
+
+	ch := &ChannelConn{
+		conn: c,
+	}
+
+	go ch.recvLoop()
+	return ch, nil
+}
+
+// NextAckHandle returns the next unique ACK handle for packet requests.
+func (ch *ChannelConn) NextAckHandle() uint32 {
+	return atomic.AddUint32(&ch.ackCounter, 1)
+}
+
+// SendPacket encrypts and sends raw packet data (including the 0x00 0x10 terminator
+// which is already appended by the Build* functions in packets.go).
+func (ch *ChannelConn) SendPacket(data []byte) error {
+	return ch.conn.SendPacket(data)
+}
+
+// WaitForAck waits for an ACK response matching the given handle.
+func (ch *ChannelConn) WaitForAck(handle uint32, timeout time.Duration) (*AckResponse, error) {
+	waitCh := make(chan *AckResponse, 1)
+	ch.waiters.Store(handle, waitCh)
+	defer ch.waiters.Delete(handle)
+
+	select {
+	case resp := <-waitCh:
+		return resp, nil
+	case <-time.After(timeout):
+		return nil, fmt.Errorf("ACK timeout for handle %d", handle)
+	}
+}
+
+// Close closes the channel connection.
+func (ch *ChannelConn) Close() error {
+	ch.closed.Store(true)
+	return ch.conn.Close()
+}
+
+// recvLoop continuously reads packets from the channel server and dispatches ACKs.
+func (ch *ChannelConn) recvLoop() {
+	for {
+		if ch.closed.Load() {
+			return
+		}
+
+		pkt, err := ch.conn.ReadPacket()
+		if err != nil {
+			if ch.closed.Load() {
+				return
+			}
+			fmt.Printf("[channel] read error: %v\n", err)
+			return
+		}
+
+		if len(pkt) < 2 {
+			continue
+		}
+
+		// Strip trailing 0x00 0x10 terminator if present for opcode parsing.
+		// Packets from server: [opcode uint16][fields...][0x00 0x10]
+		opcode := binary.BigEndian.Uint16(pkt[0:2])
+
+		switch opcode {
+		case MSG_SYS_ACK:
+			ch.handleAck(pkt[2:])
+		case MSG_SYS_PING:
+			ch.handlePing(pkt[2:])
+		default:
+			if val, ok := ch.handlers.Load(opcode); ok {
+				val.(PacketHandler)(opcode, pkt[2:])
+			} else {
+				fmt.Printf("[channel] recv opcode 0x%04X (%d bytes)\n", opcode, len(pkt))
+			}
+		}
+	}
+}
+
+// handleAck parses an ACK packet and dispatches it to a waiting caller.
+// Reference: Erupe network/mhfpacket/msg_sys_ack.go
+func (ch *ChannelConn) handleAck(data []byte) {
+	if len(data) < 8 {
+		return
+	}
+
+	ackHandle := binary.BigEndian.Uint32(data[0:4])
+	isBuffer := data[4] > 0
+	errorCode := data[5]
+
+	var ackData []byte
+	if isBuffer {
+		payloadSize := binary.BigEndian.Uint16(data[6:8])
+		offset := uint32(8)
+		if payloadSize == 0xFFFF {
+			if len(data) < 12 {
+				return
+			}
+			payloadSize32 := binary.BigEndian.Uint32(data[8:12])
+			offset = 12
+			if uint32(len(data)) >= offset+payloadSize32 {
+				ackData = data[offset : offset+payloadSize32]
+			}
+		} else {
+			if uint32(len(data)) >= offset+uint32(payloadSize) {
+				ackData = data[offset : offset+uint32(payloadSize)]
+			}
+		}
+	} else {
+		// Simple ACK: 4 bytes of data after the uint16 field.
+		if len(data) >= 12 {
+			ackData = data[8:12]
+		}
+	}
+
+	resp := &AckResponse{
+		AckHandle:        ackHandle,
+		IsBufferResponse: isBuffer,
+		ErrorCode:        errorCode,
+		Data:             ackData,
+	}
+
+	if val, ok := ch.waiters.Load(ackHandle); ok {
+		waitCh := val.(chan *AckResponse)
+		select {
+		case waitCh <- resp:
+		default:
+		}
+	} else {
+		fmt.Printf("[channel] unexpected ACK handle %d (error=%d, buffer=%v, %d bytes)\n",
+			ackHandle, errorCode, isBuffer, len(ackData))
+	}
+}
+
+// handlePing responds to a server ping to keep the connection alive.
+func (ch *ChannelConn) handlePing(data []byte) {
+	var ackHandle uint32
+	if len(data) >= 4 {
+		ackHandle = binary.BigEndian.Uint32(data[0:4])
+	}
+	pkt := BuildPingPacket(ackHandle)
+	if err := ch.conn.SendPacket(pkt); err != nil {
+		fmt.Printf("[channel] ping response failed: %v\n", err)
+	}
+}
--- a/cmd/protbot/protocol/entrance.go
+++ b/cmd/protbot/protocol/entrance.go
@@ -0,0 +1,142 @@
+package protocol
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+
+	"erupe-ce/common/byteframe"
+
+	"erupe-ce/cmd/protbot/conn"
+)
+
+// ServerEntry represents a channel server from the entrance server response.
+type ServerEntry struct {
+	IP       string
+	Port     uint16
+	Name     string
+}
+
+// DoEntrance connects to the entrance server and retrieves the server list.
+// Reference: Erupe server/entranceserver/entrance_server.go and make_resp.go.
+func DoEntrance(addr string) ([]ServerEntry, error) {
+	c, err := conn.DialWithInit(addr)
+	if err != nil {
+		return nil, fmt.Errorf("entrance connect: %w", err)
+	}
+	defer c.Close()
+
+	// Send a minimal packet (the entrance server reads it, checks len > 5 for USR data).
+	// An empty/short packet triggers only SV2 response.
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint8(0)
+	if err := c.SendPacket(bf.Data()); err != nil {
+		return nil, fmt.Errorf("entrance send: %w", err)
+	}
+
+	resp, err := c.ReadPacket()
+	if err != nil {
+		return nil, fmt.Errorf("entrance recv: %w", err)
+	}
+
+	return parseEntranceResponse(resp)
+}
+
+// parseEntranceResponse parses the Bin8-encrypted entrance server response.
+// Reference: Erupe server/entranceserver/make_resp.go (makeHeader, makeSv2Resp)
+func parseEntranceResponse(data []byte) ([]ServerEntry, error) {
+	if len(data) < 2 {
+		return nil, fmt.Errorf("entrance response too short")
+	}
+
+	// First byte is the Bin8 encryption key.
+	key := data[0]
+	decrypted := conn.DecryptBin8(data[1:], key)
+
+	rbf := byteframe.NewByteFrameFromBytes(decrypted)
+
+	// Read response type header: "SV2" or "SVR"
+	respType := string(rbf.ReadBytes(3))
+	if respType != "SV2" && respType != "SVR" {
+		return nil, fmt.Errorf("unexpected entrance response type: %s", respType)
+	}
+
+	entryCount := rbf.ReadUint16()
+	dataLen := rbf.ReadUint16()
+	if dataLen == 0 {
+		return nil, nil
+	}
+	expectedSum := rbf.ReadUint32()
+	serverData := rbf.ReadBytes(uint(dataLen))
+
+	actualSum := conn.CalcSum32(serverData)
+	if expectedSum != actualSum {
+		return nil, fmt.Errorf("entrance checksum mismatch: expected %08X, got %08X", expectedSum, actualSum)
+	}
+
+	return parseServerEntries(serverData, entryCount)
+}
+
+// parseServerEntries parses the server info binary blob.
+// Reference: Erupe server/entranceserver/make_resp.go (encodeServerInfo)
+func parseServerEntries(data []byte, entryCount uint16) ([]ServerEntry, error) {
+	bf := byteframe.NewByteFrameFromBytes(data)
+	var entries []ServerEntry
+
+	for i := uint16(0); i < entryCount; i++ {
+		ipBytes := bf.ReadBytes(4)
+		ip := net.IP([]byte{
+			byte(ipBytes[3]), byte(ipBytes[2]),
+			byte(ipBytes[1]), byte(ipBytes[0]),
+		})
+
+		_ = bf.ReadUint16() // serverIdx | 16
+		_ = bf.ReadUint16() // 0
+		channelCount := bf.ReadUint16()
+		_ = bf.ReadUint8()  // Type
+		_ = bf.ReadUint8()  // Season/rotation
+
+		// G1+ recommended flag
+		_ = bf.ReadUint8()
+
+		// G51+ (ZZ): skip 1 byte, then read 65-byte padded name
+		_ = bf.ReadUint8()
+		nameBytes := bf.ReadBytes(65)
+
+		// GG+: AllowedClientFlags
+		_ = bf.ReadUint32()
+
+		// Parse name (null-separated: name + description)
+		name := ""
+		for j := 0; j < len(nameBytes); j++ {
+			if nameBytes[j] == 0 {
+				break
+			}
+			name += string(nameBytes[j])
+		}
+
+		// Read channel entries
+		for j := uint16(0); j < channelCount; j++ {
+			port := bf.ReadUint16()
+			_ = bf.ReadUint16() // channelIdx | 16
+			_ = bf.ReadUint16() // maxPlayers
+			_ = bf.ReadUint16() // currentPlayers
+			_ = bf.ReadBytes(14) // remaining channel fields (7 x uint16)
+			_ = bf.ReadUint16() // 12345
+
+			serverIP := ip.String()
+			// Convert 127.0.0.1 representation
+			if binary.LittleEndian.Uint32(ipBytes) == 0x0100007F {
+				serverIP = "127.0.0.1"
+			}
+
+			entries = append(entries, ServerEntry{
+				IP:   serverIP,
+				Port: port,
+				Name: fmt.Sprintf("%s ch%d", name, j+1),
+			})
+		}
+	}
+
+	return entries, nil
+}
--- a/cmd/protbot/protocol/opcodes.go
+++ b/cmd/protbot/protocol/opcodes.go
@@ -0,0 +1,23 @@
+// Package protocol implements MHF network protocol message building and parsing.
+package protocol
+
+// Packet opcodes (subset from Erupe's network/packetid.go iota).
+const (
+	MSG_SYS_ACK              uint16 = 0x0012
+	MSG_SYS_LOGIN            uint16 = 0x0014
+	MSG_SYS_LOGOUT           uint16 = 0x0015
+	MSG_SYS_PING             uint16 = 0x0017
+	MSG_SYS_CAST_BINARY      uint16 = 0x0018
+	MSG_SYS_TIME             uint16 = 0x001A
+	MSG_SYS_CASTED_BINARY    uint16 = 0x001B
+	MSG_SYS_ISSUE_LOGKEY     uint16 = 0x001D
+	MSG_SYS_ENTER_STAGE      uint16 = 0x0022
+	MSG_SYS_ENUMERATE_STAGE  uint16 = 0x002F
+	MSG_SYS_INSERT_USER      uint16 = 0x0050
+	MSG_SYS_DELETE_USER      uint16 = 0x0051
+	MSG_SYS_UPDATE_RIGHT     uint16 = 0x0058
+	MSG_SYS_RIGHTS_RELOAD    uint16 = 0x005D
+	MSG_MHF_LOADDATA         uint16 = 0x0061
+	MSG_MHF_ENUMERATE_QUEST  uint16 = 0x009F
+	MSG_MHF_GET_WEEKLY_SCHED uint16 = 0x00E1
+)
--- a/cmd/protbot/protocol/packets.go
+++ b/cmd/protbot/protocol/packets.go
@@ -0,0 +1,229 @@
+package protocol
+
+import (
+	"erupe-ce/common/byteframe"
+	"erupe-ce/common/stringsupport"
+)
+
+// BuildLoginPacket builds a MSG_SYS_LOGIN packet.
+// Layout mirrors Erupe's MsgSysLogin.Parse:
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint32 charID
+//	uint32 loginTokenNumber
+//	uint16 hardcodedZero
+//	uint16 requestVersion (set to 0xCAFE as dummy)
+//	uint32 charID (repeated)
+//	uint16 zeroed
+//	uint16 always 11
+//	null-terminated tokenString
+//	0x00 0x10 terminator
+func BuildLoginPacket(ackHandle, charID, tokenNumber uint32, tokenString string) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_LOGIN)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint32(charID)
+	bf.WriteUint32(tokenNumber)
+	bf.WriteUint16(0)      // HardcodedZero0
+	bf.WriteUint16(0xCAFE) // RequestVersion (dummy)
+	bf.WriteUint32(charID) // CharID1 (repeated)
+	bf.WriteUint16(0)      // Zeroed
+	bf.WriteUint16(11)     // Always 11
+	bf.WriteNullTerminatedBytes([]byte(tokenString))
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildEnumerateStagePacket builds a MSG_SYS_ENUMERATE_STAGE packet.
+// Layout mirrors Erupe's MsgSysEnumerateStage.Parse:
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint8  always 1
+//	uint8  prefix length (including null terminator)
+//	null-terminated stagePrefix
+//	0x00 0x10 terminator
+func BuildEnumerateStagePacket(ackHandle uint32, prefix string) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_ENUMERATE_STAGE)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint8(1)                         // Always 1
+	bf.WriteUint8(uint8(len(prefix) + 1))    // Length including null terminator
+	bf.WriteNullTerminatedBytes([]byte(prefix))
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildEnterStagePacket builds a MSG_SYS_ENTER_STAGE packet.
+// Layout mirrors Erupe's MsgSysEnterStage.Parse:
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint8  isQuest (0=false)
+//	uint8  stageID length (including null terminator)
+//	null-terminated stageID
+//	0x00 0x10 terminator
+func BuildEnterStagePacket(ackHandle uint32, stageID string) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_ENTER_STAGE)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint8(0)                          // IsQuest = false
+	bf.WriteUint8(uint8(len(stageID) + 1))    // Length including null terminator
+	bf.WriteNullTerminatedBytes([]byte(stageID))
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildPingPacket builds a MSG_SYS_PING response packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	0x00 0x10 terminator
+func BuildPingPacket(ackHandle uint32) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_PING)
+	bf.WriteUint32(ackHandle)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildLogoutPacket builds a MSG_SYS_LOGOUT packet.
+//
+//	uint16 opcode
+//	uint8  logoutType (1 = normal logout)
+//	0x00 0x10 terminator
+func BuildLogoutPacket() []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_LOGOUT)
+	bf.WriteUint8(1) // LogoutType = normal
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildIssueLogkeyPacket builds a MSG_SYS_ISSUE_LOGKEY packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint16 unk0
+//	uint16 unk1
+//	0x00 0x10 terminator
+func BuildIssueLogkeyPacket(ackHandle uint32) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_ISSUE_LOGKEY)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint16(0)
+	bf.WriteUint16(0)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildRightsReloadPacket builds a MSG_SYS_RIGHTS_RELOAD packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint8  count (0 = empty)
+//	0x00 0x10 terminator
+func BuildRightsReloadPacket(ackHandle uint32) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_RIGHTS_RELOAD)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint8(0) // Count = 0 (no rights entries)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildLoaddataPacket builds a MSG_MHF_LOADDATA packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	0x00 0x10 terminator
+func BuildLoaddataPacket(ackHandle uint32) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_MHF_LOADDATA)
+	bf.WriteUint32(ackHandle)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildCastBinaryPacket builds a MSG_SYS_CAST_BINARY packet.
+// Layout mirrors Erupe's MsgSysCastBinary.Parse:
+//
+//	uint16 opcode
+//	uint32 unk (always 0)
+//	uint8  broadcastType
+//	uint8  messageType
+//	uint16 dataSize
+//	[]byte payload
+//	0x00 0x10 terminator
+func BuildCastBinaryPacket(broadcastType, messageType uint8, payload []byte) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_SYS_CAST_BINARY)
+	bf.WriteUint32(0) // Unk
+	bf.WriteUint8(broadcastType)
+	bf.WriteUint8(messageType)
+	bf.WriteUint16(uint16(len(payload)))
+	bf.WriteBytes(payload)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildChatPayload builds the inner MsgBinChat binary blob for use with BuildCastBinaryPacket.
+// Layout mirrors Erupe's binpacket/msg_bin_chat.go Build:
+//
+//	uint8  unk0 (always 0)
+//	uint8  chatType
+//	uint16 flags (always 0)
+//	uint16 senderNameLen (SJIS bytes + null terminator)
+//	uint16 messageLen (SJIS bytes + null terminator)
+//	null-terminated SJIS message
+//	null-terminated SJIS senderName
+func BuildChatPayload(chatType uint8, message, senderName string) []byte {
+	sjisMsg := stringsupport.UTF8ToSJIS(message)
+	sjisName := stringsupport.UTF8ToSJIS(senderName)
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint8(0)                              // Unk0
+	bf.WriteUint8(chatType)                       // Type
+	bf.WriteUint16(0)                             // Flags
+	bf.WriteUint16(uint16(len(sjisName) + 1))     // SenderName length (+ null term)
+	bf.WriteUint16(uint16(len(sjisMsg) + 1))      // Message length (+ null term)
+	bf.WriteNullTerminatedBytes(sjisMsg)           // Message
+	bf.WriteNullTerminatedBytes(sjisName)          // SenderName
+	return bf.Data()
+}
+
+// BuildEnumerateQuestPacket builds a MSG_MHF_ENUMERATE_QUEST packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	uint8  unk0 (always 0)
+//	uint8  world
+//	uint16 counter
+//	uint16 offset
+//	uint8  unk1 (always 0)
+//	0x00 0x10 terminator
+func BuildEnumerateQuestPacket(ackHandle uint32, world uint8, counter, offset uint16) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_MHF_ENUMERATE_QUEST)
+	bf.WriteUint32(ackHandle)
+	bf.WriteUint8(0) // Unk0
+	bf.WriteUint8(world)
+	bf.WriteUint16(counter)
+	bf.WriteUint16(offset)
+	bf.WriteUint8(0) // Unk1
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
+
+// BuildGetWeeklySchedulePacket builds a MSG_MHF_GET_WEEKLY_SCHEDULE packet.
+//
+//	uint16 opcode
+//	uint32 ackHandle
+//	0x00 0x10 terminator
+func BuildGetWeeklySchedulePacket(ackHandle uint32) []byte {
+	bf := byteframe.NewByteFrame()
+	bf.WriteUint16(MSG_MHF_GET_WEEKLY_SCHED)
+	bf.WriteUint32(ackHandle)
+	bf.WriteBytes([]byte{0x00, 0x10})
+	return bf.Data()
+}
--- a/cmd/protbot/protocol/packets_test.go
+++ b/cmd/protbot/protocol/packets_test.go
@@ -0,0 +1,412 @@
+package protocol
+
+import (
+	"encoding/binary"
+	"testing"
+
+	"erupe-ce/common/byteframe"
+)
+
+// TestBuildLoginPacket verifies that the binary layout matches Erupe's Parse.
+func TestBuildLoginPacket(t *testing.T) {
+	ackHandle := uint32(1)
+	charID := uint32(100)
+	tokenNumber := uint32(42)
+	tokenString := "0123456789ABCDEF"
+
+	pkt := BuildLoginPacket(ackHandle, charID, tokenNumber, tokenString)
+
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	opcode := bf.ReadUint16()
+	if opcode != MSG_SYS_LOGIN {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", opcode, MSG_SYS_LOGIN)
+	}
+
+	gotAck := bf.ReadUint32()
+	if gotAck != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", gotAck, ackHandle)
+	}
+
+	gotCharID0 := bf.ReadUint32()
+	if gotCharID0 != charID {
+		t.Fatalf("charID0: got %d, want %d", gotCharID0, charID)
+	}
+
+	gotTokenNum := bf.ReadUint32()
+	if gotTokenNum != tokenNumber {
+		t.Fatalf("tokenNumber: got %d, want %d", gotTokenNum, tokenNumber)
+	}
+
+	gotZero := bf.ReadUint16()
+	if gotZero != 0 {
+		t.Fatalf("hardcodedZero: got %d, want 0", gotZero)
+	}
+
+	gotVersion := bf.ReadUint16()
+	if gotVersion != 0xCAFE {
+		t.Fatalf("requestVersion: got 0x%04X, want 0xCAFE", gotVersion)
+	}
+
+	gotCharID1 := bf.ReadUint32()
+	if gotCharID1 != charID {
+		t.Fatalf("charID1: got %d, want %d", gotCharID1, charID)
+	}
+
+	gotZeroed := bf.ReadUint16()
+	if gotZeroed != 0 {
+		t.Fatalf("zeroed: got %d, want 0", gotZeroed)
+	}
+
+	gotEleven := bf.ReadUint16()
+	if gotEleven != 11 {
+		t.Fatalf("always11: got %d, want 11", gotEleven)
+	}
+
+	gotToken := string(bf.ReadNullTerminatedBytes())
+	if gotToken != tokenString {
+		t.Fatalf("tokenString: got %q, want %q", gotToken, tokenString)
+	}
+
+	// Verify terminator.
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildEnumerateStagePacket verifies binary layout matches Erupe's Parse.
+func TestBuildEnumerateStagePacket(t *testing.T) {
+	ackHandle := uint32(5)
+	prefix := "sl1Ns"
+
+	pkt := BuildEnumerateStagePacket(ackHandle, prefix)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	opcode := bf.ReadUint16()
+	if opcode != MSG_SYS_ENUMERATE_STAGE {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", opcode, MSG_SYS_ENUMERATE_STAGE)
+	}
+
+	gotAck := bf.ReadUint32()
+	if gotAck != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", gotAck, ackHandle)
+	}
+
+	alwaysOne := bf.ReadUint8()
+	if alwaysOne != 1 {
+		t.Fatalf("alwaysOne: got %d, want 1", alwaysOne)
+	}
+
+	prefixLen := bf.ReadUint8()
+	if prefixLen != uint8(len(prefix)+1) {
+		t.Fatalf("prefixLen: got %d, want %d", prefixLen, len(prefix)+1)
+	}
+
+	gotPrefix := string(bf.ReadNullTerminatedBytes())
+	if gotPrefix != prefix {
+		t.Fatalf("prefix: got %q, want %q", gotPrefix, prefix)
+	}
+
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildEnterStagePacket verifies binary layout matches Erupe's Parse.
+func TestBuildEnterStagePacket(t *testing.T) {
+	ackHandle := uint32(7)
+	stageID := "sl1Ns200p0a0u0"
+
+	pkt := BuildEnterStagePacket(ackHandle, stageID)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	opcode := bf.ReadUint16()
+	if opcode != MSG_SYS_ENTER_STAGE {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", opcode, MSG_SYS_ENTER_STAGE)
+	}
+
+	gotAck := bf.ReadUint32()
+	if gotAck != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", gotAck, ackHandle)
+	}
+
+	isQuest := bf.ReadUint8()
+	if isQuest != 0 {
+		t.Fatalf("isQuest: got %d, want 0", isQuest)
+	}
+
+	stageLen := bf.ReadUint8()
+	if stageLen != uint8(len(stageID)+1) {
+		t.Fatalf("stageLen: got %d, want %d", stageLen, len(stageID)+1)
+	}
+
+	gotStage := string(bf.ReadNullTerminatedBytes())
+	if gotStage != stageID {
+		t.Fatalf("stageID: got %q, want %q", gotStage, stageID)
+	}
+
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildPingPacket verifies MSG_SYS_PING binary layout.
+func TestBuildPingPacket(t *testing.T) {
+	ackHandle := uint32(99)
+	pkt := BuildPingPacket(ackHandle)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_SYS_PING {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_SYS_PING)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildLogoutPacket verifies MSG_SYS_LOGOUT binary layout.
+func TestBuildLogoutPacket(t *testing.T) {
+	pkt := BuildLogoutPacket()
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_SYS_LOGOUT {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_SYS_LOGOUT)
+	}
+	if lt := bf.ReadUint8(); lt != 1 {
+		t.Fatalf("logoutType: got %d, want 1", lt)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildIssueLogkeyPacket verifies MSG_SYS_ISSUE_LOGKEY binary layout.
+func TestBuildIssueLogkeyPacket(t *testing.T) {
+	ackHandle := uint32(10)
+	pkt := BuildIssueLogkeyPacket(ackHandle)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_SYS_ISSUE_LOGKEY {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_SYS_ISSUE_LOGKEY)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	if v := bf.ReadUint16(); v != 0 {
+		t.Fatalf("unk0: got %d, want 0", v)
+	}
+	if v := bf.ReadUint16(); v != 0 {
+		t.Fatalf("unk1: got %d, want 0", v)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildRightsReloadPacket verifies MSG_SYS_RIGHTS_RELOAD binary layout.
+func TestBuildRightsReloadPacket(t *testing.T) {
+	ackHandle := uint32(20)
+	pkt := BuildRightsReloadPacket(ackHandle)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_SYS_RIGHTS_RELOAD {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_SYS_RIGHTS_RELOAD)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	if c := bf.ReadUint8(); c != 0 {
+		t.Fatalf("count: got %d, want 0", c)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildLoaddataPacket verifies MSG_MHF_LOADDATA binary layout.
+func TestBuildLoaddataPacket(t *testing.T) {
+	ackHandle := uint32(30)
+	pkt := BuildLoaddataPacket(ackHandle)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_MHF_LOADDATA {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_MHF_LOADDATA)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildCastBinaryPacket verifies MSG_SYS_CAST_BINARY binary layout.
+func TestBuildCastBinaryPacket(t *testing.T) {
+	payload := []byte{0xDE, 0xAD, 0xBE, 0xEF}
+	pkt := BuildCastBinaryPacket(0x03, 1, payload)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_SYS_CAST_BINARY {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_SYS_CAST_BINARY)
+	}
+	if unk := bf.ReadUint32(); unk != 0 {
+		t.Fatalf("unk: got %d, want 0", unk)
+	}
+	if bt := bf.ReadUint8(); bt != 0x03 {
+		t.Fatalf("broadcastType: got %d, want 3", bt)
+	}
+	if mt := bf.ReadUint8(); mt != 1 {
+		t.Fatalf("messageType: got %d, want 1", mt)
+	}
+	if ds := bf.ReadUint16(); ds != uint16(len(payload)) {
+		t.Fatalf("dataSize: got %d, want %d", ds, len(payload))
+	}
+	gotPayload := bf.ReadBytes(uint(len(payload)))
+	for i, b := range payload {
+		if gotPayload[i] != b {
+			t.Fatalf("payload[%d]: got 0x%02X, want 0x%02X", i, gotPayload[i], b)
+		}
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildChatPayload verifies the MsgBinChat inner binary layout and SJIS encoding.
+func TestBuildChatPayload(t *testing.T) {
+	chatType := uint8(1)
+	message := "Hello"
+	senderName := "TestUser"
+
+	payload := BuildChatPayload(chatType, message, senderName)
+	bf := byteframe.NewByteFrameFromBytes(payload)
+
+	if unk := bf.ReadUint8(); unk != 0 {
+		t.Fatalf("unk0: got %d, want 0", unk)
+	}
+	if ct := bf.ReadUint8(); ct != chatType {
+		t.Fatalf("chatType: got %d, want %d", ct, chatType)
+	}
+	if flags := bf.ReadUint16(); flags != 0 {
+		t.Fatalf("flags: got %d, want 0", flags)
+	}
+	nameLen := bf.ReadUint16()
+	msgLen := bf.ReadUint16()
+	// "Hello" in ASCII/SJIS = 5 bytes + 1 null = 6
+	if msgLen != 6 {
+		t.Fatalf("messageLen: got %d, want 6", msgLen)
+	}
+	// "TestUser" in ASCII/SJIS = 8 bytes + 1 null = 9
+	if nameLen != 9 {
+		t.Fatalf("senderNameLen: got %d, want 9", nameLen)
+	}
+
+	gotMsg := string(bf.ReadNullTerminatedBytes())
+	if gotMsg != message {
+		t.Fatalf("message: got %q, want %q", gotMsg, message)
+	}
+	gotName := string(bf.ReadNullTerminatedBytes())
+	if gotName != senderName {
+		t.Fatalf("senderName: got %q, want %q", gotName, senderName)
+	}
+}
+
+// TestBuildEnumerateQuestPacket verifies MSG_MHF_ENUMERATE_QUEST binary layout.
+func TestBuildEnumerateQuestPacket(t *testing.T) {
+	ackHandle := uint32(40)
+	world := uint8(2)
+	counter := uint16(100)
+	offset := uint16(50)
+
+	pkt := BuildEnumerateQuestPacket(ackHandle, world, counter, offset)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_MHF_ENUMERATE_QUEST {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_MHF_ENUMERATE_QUEST)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	if u0 := bf.ReadUint8(); u0 != 0 {
+		t.Fatalf("unk0: got %d, want 0", u0)
+	}
+	if w := bf.ReadUint8(); w != world {
+		t.Fatalf("world: got %d, want %d", w, world)
+	}
+	if c := bf.ReadUint16(); c != counter {
+		t.Fatalf("counter: got %d, want %d", c, counter)
+	}
+	if o := bf.ReadUint16(); o != offset {
+		t.Fatalf("offset: got %d, want %d", o, offset)
+	}
+	if u1 := bf.ReadUint8(); u1 != 0 {
+		t.Fatalf("unk1: got %d, want 0", u1)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestBuildGetWeeklySchedulePacket verifies MSG_MHF_GET_WEEKLY_SCHEDULE binary layout.
+func TestBuildGetWeeklySchedulePacket(t *testing.T) {
+	ackHandle := uint32(50)
+	pkt := BuildGetWeeklySchedulePacket(ackHandle)
+	bf := byteframe.NewByteFrameFromBytes(pkt)
+
+	if op := bf.ReadUint16(); op != MSG_MHF_GET_WEEKLY_SCHED {
+		t.Fatalf("opcode: got 0x%04X, want 0x%04X", op, MSG_MHF_GET_WEEKLY_SCHED)
+	}
+	if ack := bf.ReadUint32(); ack != ackHandle {
+		t.Fatalf("ackHandle: got %d, want %d", ack, ackHandle)
+	}
+	term := bf.ReadBytes(2)
+	if term[0] != 0x00 || term[1] != 0x10 {
+		t.Fatalf("terminator: got %02X %02X, want 00 10", term[0], term[1])
+	}
+}
+
+// TestOpcodeValues verifies opcode constants match Erupe's iota-based enum.
+func TestOpcodeValues(t *testing.T) {
+	_ = binary.BigEndian // ensure import used
+	tests := []struct {
+		name string
+		got  uint16
+		want uint16
+	}{
+		{"MSG_SYS_ACK", MSG_SYS_ACK, 0x0012},
+		{"MSG_SYS_LOGIN", MSG_SYS_LOGIN, 0x0014},
+		{"MSG_SYS_LOGOUT", MSG_SYS_LOGOUT, 0x0015},
+		{"MSG_SYS_PING", MSG_SYS_PING, 0x0017},
+		{"MSG_SYS_CAST_BINARY", MSG_SYS_CAST_BINARY, 0x0018},
+		{"MSG_SYS_TIME", MSG_SYS_TIME, 0x001A},
+		{"MSG_SYS_CASTED_BINARY", MSG_SYS_CASTED_BINARY, 0x001B},
+		{"MSG_SYS_ISSUE_LOGKEY", MSG_SYS_ISSUE_LOGKEY, 0x001D},
+		{"MSG_SYS_ENTER_STAGE", MSG_SYS_ENTER_STAGE, 0x0022},
+		{"MSG_SYS_ENUMERATE_STAGE", MSG_SYS_ENUMERATE_STAGE, 0x002F},
+		{"MSG_SYS_INSERT_USER", MSG_SYS_INSERT_USER, 0x0050},
+		{"MSG_SYS_DELETE_USER", MSG_SYS_DELETE_USER, 0x0051},
+		{"MSG_SYS_UPDATE_RIGHT", MSG_SYS_UPDATE_RIGHT, 0x0058},
+		{"MSG_SYS_RIGHTS_RELOAD", MSG_SYS_RIGHTS_RELOAD, 0x005D},
+		{"MSG_MHF_LOADDATA", MSG_MHF_LOADDATA, 0x0061},
+		{"MSG_MHF_ENUMERATE_QUEST", MSG_MHF_ENUMERATE_QUEST, 0x009F},
+		{"MSG_MHF_GET_WEEKLY_SCHED", MSG_MHF_GET_WEEKLY_SCHED, 0x00E1},
+	}
+	for _, tt := range tests {
+		if tt.got != tt.want {
+			t.Errorf("%s: got 0x%04X, want 0x%04X", tt.name, tt.got, tt.want)
+		}
+	}
+}
--- a/cmd/protbot/protocol/sign.go
+++ b/cmd/protbot/protocol/sign.go
@@ -0,0 +1,105 @@
+package protocol
+
+import (
+	"fmt"
+
+	"erupe-ce/common/byteframe"
+	"erupe-ce/common/stringsupport"
+
+	"erupe-ce/cmd/protbot/conn"
+)
+
+// SignResult holds the parsed response from a successful DSGN sign-in.
+type SignResult struct {
+	TokenID     uint32
+	TokenString string // 16 raw bytes as string
+	Timestamp   uint32
+	EntranceAddr string
+	CharIDs     []uint32
+}
+
+// DoSign connects to the sign server and performs a DSGN login.
+// Reference: Erupe server/signserver/session.go (handleDSGN) and dsgn_resp.go (makeSignResponse).
+func DoSign(addr, username, password string) (*SignResult, error) {
+	c, err := conn.DialWithInit(addr)
+	if err != nil {
+		return nil, fmt.Errorf("sign connect: %w", err)
+	}
+	defer c.Close()
+
+	// Build DSGN request: "DSGN:\x00" + SJIS(user) + "\x00" + SJIS(pass) + "\x00" + "\x00"
+	// The server reads: null-terminated request type, null-terminated user, null-terminated pass, null-terminated unk.
+	bf := byteframe.NewByteFrame()
+	bf.WriteNullTerminatedBytes([]byte("DSGN:\x00")) // reqType (server strips last 3 chars to get "DSGN:")
+	bf.WriteNullTerminatedBytes(stringsupport.UTF8ToSJIS(username))
+	bf.WriteNullTerminatedBytes(stringsupport.UTF8ToSJIS(password))
+	bf.WriteUint8(0) // Unk null-terminated empty string
+
+	if err := c.SendPacket(bf.Data()); err != nil {
+		return nil, fmt.Errorf("sign send: %w", err)
+	}
+
+	resp, err := c.ReadPacket()
+	if err != nil {
+		return nil, fmt.Errorf("sign recv: %w", err)
+	}
+
+	return parseSignResponse(resp)
+}
+
+// parseSignResponse parses the binary response from the sign server.
+// Reference: Erupe server/signserver/dsgn_resp.go:makeSignResponse
+func parseSignResponse(data []byte) (*SignResult, error) {
+	if len(data) < 1 {
+		return nil, fmt.Errorf("empty sign response")
+	}
+
+	rbf := byteframe.NewByteFrameFromBytes(data)
+
+	resultCode := rbf.ReadUint8()
+	if resultCode != 1 { // SIGN_SUCCESS = 1
+		return nil, fmt.Errorf("sign failed with code %d", resultCode)
+	}
+
+	patchCount := rbf.ReadUint8()    // patch server count (usually 2)
+	_ = rbf.ReadUint8()              // entrance server count (usually 1)
+	charCount := rbf.ReadUint8()     // character count
+
+	result := &SignResult{}
+	result.TokenID = rbf.ReadUint32()
+	result.TokenString = string(rbf.ReadBytes(16)) // 16 raw bytes
+	result.Timestamp = rbf.ReadUint32()
+
+	// Skip patch server URLs (pascal strings with uint8 length prefix)
+	for i := uint8(0); i < patchCount; i++ {
+		strLen := rbf.ReadUint8()
+		_ = rbf.ReadBytes(uint(strLen))
+	}
+
+	// Read entrance server address (pascal string with uint8 length prefix)
+	entranceLen := rbf.ReadUint8()
+	result.EntranceAddr = string(rbf.ReadBytes(uint(entranceLen - 1)))
+	_ = rbf.ReadUint8() // null terminator
+
+	// Read character entries
+	for i := uint8(0); i < charCount; i++ {
+		charID := rbf.ReadUint32()
+		result.CharIDs = append(result.CharIDs, charID)
+
+		_ = rbf.ReadUint16() // HR
+		_ = rbf.ReadUint16() // WeaponType
+		_ = rbf.ReadUint32() // LastLogin
+		_ = rbf.ReadUint8()  // IsFemale
+		_ = rbf.ReadUint8()  // IsNewCharacter
+		_ = rbf.ReadUint8()  // Old GR
+		_ = rbf.ReadUint8()  // Use uint16 GR flag
+		_ = rbf.ReadBytes(16) // Character name (padded)
+		_ = rbf.ReadBytes(32) // Unk desc string (padded)
+		// ZZ mode: additional fields
+		_ = rbf.ReadUint16() // GR
+		_ = rbf.ReadUint8()  // Unk
+		_ = rbf.ReadUint8()  // Unk
+	}
+
+	return result, nil
+}
--- a/cmd/protbot/scenario/chat.go
+++ b/cmd/protbot/scenario/chat.go
@@ -0,0 +1,74 @@
+package scenario
+
+import (
+	"fmt"
+
+	"erupe-ce/common/byteframe"
+	"erupe-ce/common/stringsupport"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// ChatMessage holds a parsed incoming chat message.
+type ChatMessage struct {
+	ChatType   uint8
+	SenderName string
+	Message    string
+}
+
+// SendChat sends a chat message via MSG_SYS_CAST_BINARY with a MsgBinChat payload.
+// broadcastType controls delivery scope: 0x03 = stage, 0x06 = world.
+func SendChat(ch *protocol.ChannelConn, broadcastType, chatType uint8, message, senderName string) error {
+	payload := protocol.BuildChatPayload(chatType, message, senderName)
+	pkt := protocol.BuildCastBinaryPacket(broadcastType, 1, payload)
+	fmt.Printf("[chat] Sending chat (type=%d, broadcast=%d): %s\n", chatType, broadcastType, message)
+	return ch.SendPacket(pkt)
+}
+
+// ChatCallback is invoked when a chat message is received.
+type ChatCallback func(msg ChatMessage)
+
+// ListenChat registers a handler on MSG_SYS_CASTED_BINARY that parses chat
+// messages (messageType=1) and invokes the callback.
+func ListenChat(ch *protocol.ChannelConn, cb ChatCallback) {
+	ch.OnPacket(protocol.MSG_SYS_CASTED_BINARY, func(opcode uint16, data []byte) {
+		// MSG_SYS_CASTED_BINARY layout from server:
+		//   uint32 unk
+		//   uint8  broadcastType
+		//   uint8  messageType
+		//   uint16 dataSize
+		//   []byte payload
+		if len(data) < 8 {
+			return
+		}
+		messageType := data[5]
+		if messageType != 1 { // Only handle chat messages.
+			return
+		}
+		bf := byteframe.NewByteFrameFromBytes(data)
+		_ = bf.ReadUint32() // unk
+		_ = bf.ReadUint8()  // broadcastType
+		_ = bf.ReadUint8()  // messageType
+		dataSize := bf.ReadUint16()
+		if dataSize == 0 {
+			return
+		}
+		payload := bf.ReadBytes(uint(dataSize))
+
+		// Parse MsgBinChat inner payload.
+		pbf := byteframe.NewByteFrameFromBytes(payload)
+		_ = pbf.ReadUint8()  // unk0
+		chatType := pbf.ReadUint8()
+		_ = pbf.ReadUint16() // flags
+		_ = pbf.ReadUint16() // senderNameLen
+		_ = pbf.ReadUint16() // messageLen
+		msg := stringsupport.SJISToUTF8(pbf.ReadNullTerminatedBytes())
+		sender := stringsupport.SJISToUTF8(pbf.ReadNullTerminatedBytes())
+
+		cb(ChatMessage{
+			ChatType:   chatType,
+			SenderName: sender,
+			Message:    msg,
+		})
+	})
+}
--- a/cmd/protbot/scenario/login.go
+++ b/cmd/protbot/scenario/login.go
@@ -0,0 +1,82 @@
+// Package scenario provides high-level MHF protocol flows.
+package scenario
+
+import (
+	"fmt"
+	"time"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// LoginResult holds the outcome of a full login flow.
+type LoginResult struct {
+	Sign    *protocol.SignResult
+	Servers []protocol.ServerEntry
+	Channel *protocol.ChannelConn
+}
+
+// Login performs the full sign → entrance → channel login flow.
+func Login(signAddr, username, password string) (*LoginResult, error) {
+	// Step 1: Sign server authentication.
+	fmt.Printf("[sign] Connecting to %s...\n", signAddr)
+	sign, err := protocol.DoSign(signAddr, username, password)
+	if err != nil {
+		return nil, fmt.Errorf("sign: %w", err)
+	}
+	fmt.Printf("[sign] OK — tokenID=%d, %d character(s), entrance=%s\n",
+		sign.TokenID, len(sign.CharIDs), sign.EntranceAddr)
+
+	if len(sign.CharIDs) == 0 {
+		return nil, fmt.Errorf("no characters on account")
+	}
+
+	// Step 2: Entrance server — get server/channel list.
+	fmt.Printf("[entrance] Connecting to %s...\n", sign.EntranceAddr)
+	servers, err := protocol.DoEntrance(sign.EntranceAddr)
+	if err != nil {
+		return nil, fmt.Errorf("entrance: %w", err)
+	}
+	if len(servers) == 0 {
+		return nil, fmt.Errorf("no channels available")
+	}
+	for i, s := range servers {
+		fmt.Printf("[entrance]   [%d] %s — %s:%d\n", i, s.Name, s.IP, s.Port)
+	}
+
+	// Step 3: Connect to the first channel server.
+	first := servers[0]
+	channelAddr := fmt.Sprintf("%s:%d", first.IP, first.Port)
+	fmt.Printf("[channel] Connecting to %s...\n", channelAddr)
+	ch, err := protocol.ConnectChannel(channelAddr)
+	if err != nil {
+		return nil, fmt.Errorf("channel connect: %w", err)
+	}
+
+	// Step 4: Send MSG_SYS_LOGIN.
+	charID := sign.CharIDs[0]
+	ack := ch.NextAckHandle()
+	loginPkt := protocol.BuildLoginPacket(ack, charID, sign.TokenID, sign.TokenString)
+	fmt.Printf("[channel] Sending MSG_SYS_LOGIN (charID=%d, ackHandle=%d)...\n", charID, ack)
+	if err := ch.SendPacket(loginPkt); err != nil {
+		ch.Close()
+		return nil, fmt.Errorf("channel send login: %w", err)
+	}
+
+	resp, err := ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		ch.Close()
+		return nil, fmt.Errorf("channel login ack: %w", err)
+	}
+	if resp.ErrorCode != 0 {
+		ch.Close()
+		return nil, fmt.Errorf("channel login failed: error code %d", resp.ErrorCode)
+	}
+	fmt.Printf("[channel] Login ACK received (error=%d, %d bytes data)\n",
+		resp.ErrorCode, len(resp.Data))
+
+	return &LoginResult{
+		Sign:    sign,
+		Servers: servers,
+		Channel: ch,
+	}, nil
+}
--- a/cmd/protbot/scenario/logout.go
+++ b/cmd/protbot/scenario/logout.go
@@ -0,0 +1,17 @@
+package scenario
+
+import (
+	"fmt"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// Logout sends MSG_SYS_LOGOUT and closes the channel connection.
+func Logout(ch *protocol.ChannelConn) error {
+	fmt.Println("[logout] Sending MSG_SYS_LOGOUT...")
+	if err := ch.SendPacket(protocol.BuildLogoutPacket()); err != nil {
+		ch.Close()
+		return fmt.Errorf("logout send: %w", err)
+	}
+	return ch.Close()
+}
--- a/cmd/protbot/scenario/quest.go
+++ b/cmd/protbot/scenario/quest.go
@@ -0,0 +1,31 @@
+package scenario
+
+import (
+	"fmt"
+	"time"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// EnumerateQuests sends MSG_MHF_ENUMERATE_QUEST and returns the raw quest list data.
+func EnumerateQuests(ch *protocol.ChannelConn, world uint8, counter uint16) ([]byte, error) {
+	ack := ch.NextAckHandle()
+	pkt := protocol.BuildEnumerateQuestPacket(ack, world, counter, 0)
+	fmt.Printf("[quest] Sending MSG_MHF_ENUMERATE_QUEST (world=%d, counter=%d, ackHandle=%d)...\n",
+		world, counter, ack)
+	if err := ch.SendPacket(pkt); err != nil {
+		return nil, fmt.Errorf("enumerate quest send: %w", err)
+	}
+
+	resp, err := ch.WaitForAck(ack, 15*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("enumerate quest ack: %w", err)
+	}
+	if resp.ErrorCode != 0 {
+		return nil, fmt.Errorf("enumerate quest failed: error code %d", resp.ErrorCode)
+	}
+	fmt.Printf("[quest] ENUMERATE_QUEST ACK (error=%d, %d bytes data)\n",
+		resp.ErrorCode, len(resp.Data))
+
+	return resp.Data, nil
+}
--- a/cmd/protbot/scenario/session.go
+++ b/cmd/protbot/scenario/session.go
@@ -0,0 +1,50 @@
+package scenario
+
+import (
+	"fmt"
+	"time"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// SetupSession performs the post-login session setup: ISSUE_LOGKEY, RIGHTS_RELOAD, LOADDATA.
+// Returns the loaddata response blob for inspection.
+func SetupSession(ch *protocol.ChannelConn, charID uint32) ([]byte, error) {
+	// Step 1: Issue logkey.
+	ack := ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_SYS_ISSUE_LOGKEY (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildIssueLogkeyPacket(ack)); err != nil {
+		return nil, fmt.Errorf("issue logkey send: %w", err)
+	}
+	resp, err := ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("issue logkey ack: %w", err)
+	}
+	fmt.Printf("[session] ISSUE_LOGKEY ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	// Step 2: Rights reload.
+	ack = ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_SYS_RIGHTS_RELOAD (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildRightsReloadPacket(ack)); err != nil {
+		return nil, fmt.Errorf("rights reload send: %w", err)
+	}
+	resp, err = ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("rights reload ack: %w", err)
+	}
+	fmt.Printf("[session] RIGHTS_RELOAD ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	// Step 3: Load save data.
+	ack = ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_MHF_LOADDATA (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildLoaddataPacket(ack)); err != nil {
+		return nil, fmt.Errorf("loaddata send: %w", err)
+	}
+	resp, err = ch.WaitForAck(ack, 30*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("loaddata ack: %w", err)
+	}
+	fmt.Printf("[session] LOADDATA ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	return resp.Data, nil
+}
--- a/cmd/protbot/scenario/stage.go
+++ b/cmd/protbot/scenario/stage.go
@@ -0,0 +1,111 @@
+package scenario
+
+import (
+	"encoding/binary"
+	"fmt"
+	"time"
+
+	"erupe-ce/common/byteframe"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// StageInfo holds a parsed stage entry from MSG_SYS_ENUMERATE_STAGE response.
+type StageInfo struct {
+	ID         string
+	Reserved   uint16
+	Clients    uint16
+	Displayed  uint16
+	MaxPlayers uint16
+	Flags      uint8
+}
+
+// EnterLobby enumerates available lobby stages and enters the first one.
+func EnterLobby(ch *protocol.ChannelConn) error {
+	// Step 1: Enumerate stages with "sl1Ns" prefix (main lobby stages).
+	ack := ch.NextAckHandle()
+	enumPkt := protocol.BuildEnumerateStagePacket(ack, "sl1Ns")
+	fmt.Printf("[stage] Sending MSG_SYS_ENUMERATE_STAGE (prefix=\"sl1Ns\", ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(enumPkt); err != nil {
+		return fmt.Errorf("enumerate stage send: %w", err)
+	}
+
+	resp, err := ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return fmt.Errorf("enumerate stage ack: %w", err)
+	}
+	if resp.ErrorCode != 0 {
+		return fmt.Errorf("enumerate stage failed: error code %d", resp.ErrorCode)
+	}
+
+	stages := parseEnumerateStageResponse(resp.Data)
+	fmt.Printf("[stage] Found %d stage(s)\n", len(stages))
+	for i, s := range stages {
+		fmt.Printf("[stage]   [%d] %s — %d/%d players, flags=0x%02X\n",
+			i, s.ID, s.Clients, s.MaxPlayers, s.Flags)
+	}
+
+	// Step 2: Enter the default lobby stage.
+	// Even if no stages were enumerated, use the default stage ID.
+	stageID := "sl1Ns200p0a0u0"
+	if len(stages) > 0 {
+		stageID = stages[0].ID
+	}
+
+	ack = ch.NextAckHandle()
+	enterPkt := protocol.BuildEnterStagePacket(ack, stageID)
+	fmt.Printf("[stage] Sending MSG_SYS_ENTER_STAGE (stageID=%q, ackHandle=%d)...\n", stageID, ack)
+	if err := ch.SendPacket(enterPkt); err != nil {
+		return fmt.Errorf("enter stage send: %w", err)
+	}
+
+	resp, err = ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return fmt.Errorf("enter stage ack: %w", err)
+	}
+	if resp.ErrorCode != 0 {
+		return fmt.Errorf("enter stage failed: error code %d", resp.ErrorCode)
+	}
+	fmt.Printf("[stage] Enter stage ACK received (error=%d)\n", resp.ErrorCode)
+
+	return nil
+}
+
+// parseEnumerateStageResponse parses the ACK data from MSG_SYS_ENUMERATE_STAGE.
+// Reference: Erupe server/channelserver/handlers_stage.go (handleMsgSysEnumerateStage)
+func parseEnumerateStageResponse(data []byte) []StageInfo {
+	if len(data) < 2 {
+		return nil
+	}
+
+	bf := byteframe.NewByteFrameFromBytes(data)
+	count := bf.ReadUint16()
+
+	var stages []StageInfo
+	for i := uint16(0); i < count; i++ {
+		s := StageInfo{}
+		s.Reserved = bf.ReadUint16()
+		s.Clients = bf.ReadUint16()
+		s.Displayed = bf.ReadUint16()
+		s.MaxPlayers = bf.ReadUint16()
+		s.Flags = bf.ReadUint8()
+
+		// Stage ID is a pascal string with uint8 length prefix.
+		strLen := bf.ReadUint8()
+		if strLen > 0 {
+			idBytes := bf.ReadBytes(uint(strLen))
+			// Remove null terminator if present.
+			if len(idBytes) > 0 && idBytes[len(idBytes)-1] == 0 {
+				idBytes = idBytes[:len(idBytes)-1]
+			}
+			s.ID = string(idBytes)
+		}
+
+		stages = append(stages, s)
+	}
+
+	// After stages: uint32 timestamp, uint32 max clan members (we ignore these).
+	_ = binary.BigEndian // suppress unused import if needed
+
+	return stages
+}