Fix asio port sharing options (#203)

* Windows: explicitly set the special SO_EXCLUSIVEADDRUSE flag
* changelog

2 files changed, 32 insertions, 9 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8bcd92fa..22f71bb56 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,17 +1,18 @@
 ##
-- Feature: Recording and playback of cache request with full data - both get and put operations can be replayed. Invoke via web request.
+- Feature: Recording and playback of cache request with full data - both get and put operations can be replayed. Invoke via web request
   - `<host>/z$/exec$/start-recording?<disk-storage-path>`
   - `<host>/z$/exec$/stop-recording`
   - `<host>/z$/exec$/replay-recording?<thread-count>&<disk-storage-path>`
-- Feature: Disk size triggered GC, a soft disk usage limit for cache data.
-- Feature: New option `--gc-disk-size-soft-limit` (command line), `gc.cache.disksizesoftlimit` (lua config) controlling limit for soft disk usage limit. Defaults to zero which disables soft disk usage limit.
-- Improvement: Disk write pressure in GC log and cleaned up clutter in GC logging.
-- Improvement: Much improved performance, between 2x to 9x improvement under heavy load (excluding http service overhead). See https://github.com/EpicGames/zen/pull/200 for details.
+- Feature: Disk size triggered GC, a soft disk usage limit for cache data
+- Feature: New option `--gc-disk-size-soft-limit` (command line), `gc.cache.disksizesoftlimit` (lua config) controlling limit for soft disk usage limit. Defaults to zero which disables soft disk usage limit
+- Improvement: Disk write pressure in GC log and cleaned up clutter in GC logging
+- Improvement: Much improved performance, between 2x to 9x improvement under heavy load (excluding http service overhead). See https://github.com/EpicGames/zen/pull/200 for details
 - Bugfix: Always store records or oplog entries before storing attachments to avoid GC finding unreferenced chunks i CidStore
 - Bugfix: Updated Zen `drop` command to support namespaces
 - Bugfix: Use ZEN_CONSOLE for output to console in Zen commands
 - Bugfix: Zen `status` command now shows info about found Zen instances
 - Bugfix: Zen `top` command now shows session id string
+- Bugfix: On Windows platforms explicitly set the special `SO_EXCLUSIVEADDRUSE` flag as `SO_REUSEADDR` still allows shared use of sockets
 - Changed: Reduced GC `INFO` spam by converting to `DEBUG` log messages
 - Changed: Use Iso8601 format for logging start and end message
 
diff --git a/zenhttp/httpasio.cpp b/zenhttp/httpasio.cpp
index 39a363711..68984c86d 100644
--- a/zenhttp/httpasio.cpp
+++ b/zenhttp/httpasio.cpp
@@ -932,22 +932,42 @@ HttpRequest::OnMessageComplete()
 
 struct HttpAcceptor
 {
-	HttpAcceptor(HttpAsioServerImpl& Server, asio::io_service& IoService, uint16_t Port)
+	HttpAcceptor(HttpAsioServerImpl& Server, asio::io_service& IoService, uint16_t BasePort)
 	: m_Server(Server)
 	, m_IoService(IoService)
 	, m_Acceptor(m_IoService, asio::ip::tcp::v6())
 	{
 		m_Acceptor.set_option(asio::ip::v6_only(false));
-		m_Acceptor.set_option(asio::socket_base::reuse_address(true));
+#if ZEN_PLATFORM_WINDOWS
+		// Special option for Windows settings as !asio::socket_base::reuse_address is not the same as exclusive access on Windows platforms
+		typedef asio::detail::socket_option::boolean<ASIO_OS_DEF(SOL_SOCKET), SO_EXCLUSIVEADDRUSE> excluse_address;
+		m_Acceptor.set_option(excluse_address(true));
+#else	// ZEN_PLATFORM_WINDOWS
+		m_Acceptor.set_option(asio::socket_base::reuse_address(false));
+#endif	// ZEN_PLATFORM_WINDOWS
+
 		m_Acceptor.set_option(asio::ip::tcp::no_delay(true));
 		m_Acceptor.set_option(asio::socket_base::receive_buffer_size(128 * 1024));
 		m_Acceptor.set_option(asio::socket_base::send_buffer_size(256 * 1024));
 
+		uint16_t EffectivePort = BasePort;
+
 		asio::error_code BindErrorCode;
-		m_Acceptor.bind(asio::ip::tcp::endpoint(asio::ip::address_v6::any(), Port), BindErrorCode);
+		m_Acceptor.bind(asio::ip::tcp::endpoint(asio::ip::address_v6::any(), EffectivePort), BindErrorCode);
+		// Sharing violation implies the port is being used by another process
+		for (uint16_t PortOffset = 1; (BindErrorCode == asio::error::address_in_use) && (PortOffset < 10); ++PortOffset)
+		{
+			EffectivePort = BasePort + (PortOffset * 100);
+			m_Acceptor.bind(asio::ip::tcp::endpoint(asio::ip::address_v6::any(), EffectivePort), BindErrorCode);
+		}
 		if (BindErrorCode == asio::error::access_denied)
 		{
-			m_Acceptor.bind(asio::ip::tcp::endpoint(asio::ip::address_v6::any(), 0));
+			EffectivePort = 0;
+			m_Acceptor.bind(asio::ip::tcp::endpoint(asio::ip::address_v6::any(), EffectivePort), BindErrorCode);
+		}
+		if (BindErrorCode)
+		{
+			ZEN_ERROR("Unable open asio service, error '{}'", BindErrorCode.message());
 		}
 
 #if ZEN_PLATFORM_WINDOWS
@@ -969,6 +989,8 @@ struct HttpAcceptor
 				 0);
 #endif
 		m_Acceptor.listen();
+
+		ZEN_INFO("Started asio server at port '{}'", EffectivePort);
 	}
 
 	void Start()