fix(pymsg): add recv_timeout to MsgServer to prevent Slowloris DoS

- Add configurable recv_timeout (default 10s) to MsgServer
- _handle_client now uses recv(s, timeout=...) instead of infinite blocking recv(s)
- Catch TimeoutError and close the slow client connection
- This prevents a single stalled connection from blocking the entire main select loop
- Update README with recv_timeout parameter and Slowloris mitigation docs
- Backward compatible: keyword-only arg with sensible default

pymsg/README.md

@@ -142,6 +142,7 @@ server.start(on_message)   # 阻塞当前线程
 | `addr` | 监听地址 |
 | `port` | 监听端口 |
 | `workers` | 工作线程数（关键字参数，默认 `0`）；`>0` 时回调在线程池中并发执行 |
+| `recv_timeout` | 接收单条客户端消息的超时秒数（关键字参数，默认 `10.0`）；超时未收到完整消息则主动断开连接，防御 Slowloris 式半开连接攻击 |
 
 回调签名为 `on_message(sock, addr, text)`：
 - `sock` — 客户端 socket，可用 `reply()` 回复
@@ -160,6 +161,8 @@ server.start(on_message)   # 阻塞当前线程
 
 服务端内部管理客户端列表，透明处理断连和管道破裂，使用 `select` 实现非阻塞 I/O，轮询间隔 100ms。
 
+**Slowloris 防护**：每个客户端连接在 `recv_timeout`（默认 10 秒）内必须发送完一条完整消息（4 字节头 + 载荷），超时未完成则服务端主动断开该连接，防止慢速发送攻击阻塞主事件循环。
+
 **并发模式（v0.2.0）**：
 
 ```python

pymsg/pymsg/__init__.py

@@ -296,10 +296,14 @@ class MsgServer:
     经每连接发送锁串行化，不会发生帧交错。
     """
 
-    def __init__(self, addr: str, port: int, *, workers: int = 0) -> None:
+    _RECV_TIMEOUT = 10.0  # 服务端接收单条消息的超时（秒），防止 Slowloris 式半开连接卡死主线程
+
+    def __init__(self, addr: str, port: int, *, workers: int = 0,
+                 recv_timeout: float = _RECV_TIMEOUT) -> None:
         self.addr = addr
         self.port = port
         self._workers = workers
+        self._recv_timeout = recv_timeout
         self._running = False
         self._server_sock: "_socket.socket | None" = None
         self._clients: "dict" = {}          # socket -> (ip, port)
@@ -429,8 +433,9 @@ class MsgServer:
 
     def _handle_client(self, s, socketlist, on_message):
         try:
-            text = recv(s)
-        except (ConnectionError, ConnectionResetError, OSError):
+            text = recv(s, timeout=self._recv_timeout)
+        except (ConnectionError, ConnectionResetError, OSError, TimeoutError):
+            # TimeoutError: 客户端在超时时间内未发送完整消息（Slowloris 防护），关闭连接
             self._remove_client(s, socketlist)
             return
         addr = self._clients.get(s, ("unknown", 0))