feat: 实现 Python 与 Java SDK 连接收发及其余接口

sdk/python/src/nixmsg/errors.py

@@ -0,0 +1,20 @@
+"""NixMsg SDK 错误。"""
+
+from __future__ import annotations
+
+
+class NixMsgError(Exception):
+    def __init__(self, code: str, message: str = "") -> None:
+        self.code = code
+        self.message = message or code
+        super().__init__(self.message)
+
+
+class NotConnectedError(NixMsgError):
+    def __init__(self, message: str = "未连接") -> None:
+        super().__init__("not_connected", message)
+
+
+class ClosedError(NixMsgError):
+    def __init__(self, message: str = "已关闭") -> None:
+        super().__init__("closed", message)