Add SO_REUSEPORT socket option for faster port reuse in tests

On Linux/macOS, SO_REUSEPORT allows multiple sockets to bind to the
same port, which helps prevent "Address already in use" errors when
tests run in quick succession and ports are still in TIME_WAIT state.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: gijzelaerr

snap7/partner.py

@@ -535,6 +535,9 @@ def _start_listening(self) -> None:
         """Start listening for incoming connections (passive mode)."""
         self._server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         self._server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        # Try to use SO_REUSEPORT if available (Linux, macOS) for faster port reuse
+        if hasattr(socket, "SO_REUSEPORT"):
+            self._server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
         self._server_socket.bind((self.local_ip, self.port))
         self._server_socket.listen(1)
         self._server_socket.settimeout(1.0)  # Allow periodic check

snap7/server.py

@@ -120,6 +120,9 @@ def start(self, tcp_port: int = 102) -> int:
         self.port = tcp_port
         self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        # Try to use SO_REUSEPORT if available (Linux, macOS) for faster port reuse
+        if hasattr(socket, "SO_REUSEPORT"):
+            self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
 
         try:
             self.server_socket.bind((self.host, self.port))