diff --git a/signaling_server.py b/signaling_server.py
new file mode 100644
index 0000000..caa532a
--- /dev/null
+++ b/signaling_server.py
@@ -0,0 +1,289 @@
+"""
+信令服务器
+负责帮助客户端找到对方的连接信息（IP + 端口）
+不传输实际文件，只传输元信息
+"""
+import socket
+import threading
+import json
+import time
+from typing import Dict, Optional
+
+
+class SignalingServer:
+    """信令服务器类"""
+    
+    def __init__(self, host: str = '0.0.0.0', port: int = 9999):
+        """
+        初始化信令服务器
+        
+        Args:
+            host: 监听地址，默认 0.0.0.0（监听所有网卡）
+            port: 监听端口，默认 9999
+        """
+        self.host = host
+        self.port = port
+        self.server_socket: Optional[socket.socket] = None
+        self.running = False
+        
+        # 在线用户字典：{user_id: {"ip": "x.x.x.x", "port": xxxx, "last_seen": timestamp}}
+        self.online_users: Dict[str, dict] = {}
+        self.users_lock = threading.Lock()
+        
+    def start(self):
+        """启动信令服务器"""
+        try:
+            self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            self.server_socket.bind((self.host, self.port))
+            self.server_socket.listen(5)
+            # 设置超时，防止 accept() 无限阻塞
+            self.server_socket.settimeout(1.0)
+            self.running = True
+            
+            print(f"[信令服务器] 启动成功，监听 {self.host}:{self.port}")
+            print(f"[信令服务器] 等待客户端连接...")
+            
+            # 启动心跳检测线程（可选）
+            heartbeat_thread = threading.Thread(target=self._heartbeat_checker, daemon=True)
+            heartbeat_thread.start()
+            
+            # 主循环：接受客户端连接
+            while self.running:
+                try:
+                    client_socket, client_address = self.server_socket.accept()
+                    print(f"[信令服务器] 新连接来自 {client_address}")
+                    
+                    # 为每个客户端创建处理线程
+                    client_thread = threading.Thread(
+                        target=self._handle_client,
+                        args=(client_socket, client_address),
+                        daemon=True
+                    )
+                    client_thread.start()
+                    
+                except socket.timeout:
+                    # 超时是正常的，继续循环以检查 running 标志
+                    continue
+                except Exception as e:
+                    if self.running:
+                        print(f"[信令服务器] 接受连接时出错: {e}")
+                        
+        except Exception as e:
+            print(f"[信令服务器] 启动失败: {e}")
+            self.running = False
+            
+    def _handle_client(self, client_socket: socket.socket, client_address: tuple):
+        """
+        处理客户端请求
+        
+        Args:
+            client_socket: 客户端套接字
+            client_address: 客户端地址
+        """
+        try:
+            # 接收请求数据
+            data = client_socket.recv(4096).decode('utf-8')
+            if not data:
+                return
+                
+            request = json.loads(data)
+            request_type = request.get('type')
+            
+            print(f"[信令服务器] 收到请求: {request_type} 来自 {client_address}")
+            
+            # 根据请求类型分发处理
+            if request_type == 'register':
+                response = self._handle_register(request, client_address)
+            elif request_type == 'query':
+                response = self._handle_query(request)
+            elif request_type == 'unregister':
+                response = self._handle_unregister(request)
+            elif request_type == 'list':
+                response = self._handle_list()
+            else:
+                response = {
+                    'status': 'error',
+                    'message': f'未知的请求类型: {request_type}'
+                }
+            
+            # 发送响应
+            client_socket.send(json.dumps(response).encode('utf-8'))
+            
+        except json.JSONDecodeError:
+            error_response = {'status': 'error', 'message': '无效的 JSON 格式'}
+            client_socket.send(json.dumps(error_response).encode('utf-8'))
+        except Exception as e:
+            print(f"[信令服务器] 处理客户端请求时出错: {e}")
+            error_response = {'status': 'error', 'message': str(e)}
+            try:
+                client_socket.send(json.dumps(error_response).encode('utf-8'))
+            except:
+                pass
+        finally:
+            client_socket.close()
+            
+    def _handle_register(self, request: dict, client_address: tuple) -> dict:
+        """
+        处理用户注册请求
+        
+        Args:
+            request: 请求数据 {"type": "register", "user_id": "alice", "listen_port": 8001}
+            client_address: 客户端地址
+            
+        Returns:
+            响应数据
+        """
+        user_id = request.get('user_id')
+        listen_port = request.get('listen_port')
+        
+        if not user_id or not listen_port:
+            return {'status': 'error', 'message': '缺少 user_id 或 listen_port'}
+        
+        # 获取客户端的真实 IP
+        client_ip = client_address[0]
+        
+        with self.users_lock:
+            # 检查用户是否已经注册
+            if user_id in self.online_users:
+                print(f"[信令服务器] 用户 {user_id} 重复注册，更新信息")
+            
+            # 注册或更新用户信息
+            self.online_users[user_id] = {
+                'ip': client_ip,
+                'port': listen_port,
+                'last_seen': time.time()
+            }
+            
+        print(f"[信令服务器] 用户 {user_id} 注册成功: {client_ip}:{listen_port}")
+        print(f"[信令服务器] 当前在线用户: {list(self.online_users.keys())}")
+        
+        return {
+            'status': 'success',
+            'message': '注册成功',
+            'user_id': user_id,
+            'ip': client_ip,
+            'port': listen_port
+        }
+    
+    def _handle_query(self, request: dict) -> dict:
+        """
+        处理查询对方信息的请求
+        
+        Args:
+            request: 请求数据 {"type": "query", "target_user": "bob"}
+            
+        Returns:
+            响应数据
+        """
+        target_user = request.get('target_user')
+        
+        if not target_user:
+            return {'status': 'error', 'message': '缺少 target_user'}
+        
+        with self.users_lock:
+            if target_user not in self.online_users:
+                return {
+                    'status': 'error',
+                    'message': f'用户 {target_user} 不在线'
+                }
+            
+            user_info = self.online_users[target_user]
+            
+        print(f"[信令服务器] 查询用户 {target_user}: {user_info['ip']}:{user_info['port']}")
+        
+        return {
+            'status': 'success',
+            'user_id': target_user,
+            'ip': user_info['ip'],
+            'port': user_info['port']
+        }
+    
+    def _handle_unregister(self, request: dict) -> dict:
+        """
+        处理用户注销请求
+        
+        Args:
+            request: 请求数据 {"type": "unregister", "user_id": "alice"}
+            
+        Returns:
+            响应数据
+        """
+        user_id = request.get('user_id')
+        
+        if not user_id:
+            return {'status': 'error', 'message': '缺少 user_id'}
+        
+        with self.users_lock:
+            if user_id in self.online_users:
+                del self.online_users[user_id]
+                print(f"[信令服务器] 用户 {user_id} 已注销")
+                print(f"[信令服务器] 当前在线用户: {list(self.online_users.keys())}")
+                return {'status': 'success', 'message': '注销成功'}
+            else:
+                return {'status': 'error', 'message': f'用户 {user_id} 不存在'}
+    
+    def _handle_list(self) -> dict:
+        """
+        处理获取在线用户列表的请求
+        
+        Returns:
+            响应数据
+        """
+        with self.users_lock:
+            users = list(self.online_users.keys())
+        
+        print(f"[信令服务器] 返回在线用户列表: {users}")
+        
+        return {
+            'status': 'success',
+            'users': users,
+            'count': len(users)
+        }
+    
+    def _heartbeat_checker(self):
+        """
+        心跳检测线程，定期清理超时用户（超过 5 分钟未更新）
+        """
+        timeout = 300  # 5 分钟超时
+        
+        while self.running:
+            time.sleep(60)  # 每分钟检查一次
+            
+            current_time = time.time()
+            with self.users_lock:
+                timeout_users = [
+                    user_id for user_id, info in self.online_users.items()
+                    if current_time - info['last_seen'] > timeout
+                ]
+                
+                for user_id in timeout_users:
+                    del self.online_users[user_id]
+                    print(f"[信令服务器] 用户 {user_id} 超时，已移除")
+    
+    def stop(self):
+        """停止信令服务器"""
+        print("[信令服务器] 正在关闭...")
+        self.running = False
+        
+        if self.server_socket:
+            self.server_socket.close()
+        
+        print("[信令服务器] 已关闭")
+
+
+def main():
+    """
+    启动信令服务器
+    """
+    server = SignalingServer(host='0.0.0.0', port=9999)
+    
+    try:
+        server.start()
+    except KeyboardInterrupt:
+        print("\n[信令服务器] 收到退出信号")
+        server.stop()
+
+
+if __name__ == "__main__":
+    main()