Supported by
*Requires custom Indy version.
IOCP for Windows is an API that allows handling thousands of connections using a limited pool of threads instead of using one thread per connection as Indy does by default.
To enable IOCP for Indy Servers, Go to IOHandlerOptions property and select iohIOCP as IOHandler Type.
Server.IOHandlerOptions.IOHandlerType := iohIOCP;
Server.IOHandlerOptions.IOCP.IOCPThreads := 0;
Server.IOHandlerOptions.IOCP.WorkOpThreads := 0;
IOCPThreads are the threads used for IOCP asynchronous requests (overlapped operations), by default the value is zero which means the number of threads are calculated using the number of processors (except for Delphi 7 and 2007 where the number of threads is set to 32 because the function cpucount is not supported).
WorkOpThreads should only be enabled if you want connections to always be processed in the same thread. When using IOCP, the requests are processed by a pool of threads, and every request (for the same connection) can be processed in different threads. If you want to handle every connection in the same thread set in WorkOpThreads the number of threads used to handle these requests. This impacts the performance of the server and it is only recommended to set a value greater than zero if you require this feature.
Enabling IOCP for windows servers is recommended when you need to handle thousands of connections. If your server is only handling a maximum of 100 concurrent connections, you can stay with the default Indy thread model.
OnDisconnect event not fired
IOCP works differently from default indy IOHandler. With the default Indy IOHandler, every connection runs in a thread and these threads are running all the time, checking if the connection is active, so if there is a disconnection, it's notified in a short period of time.
IOCP works differently, there is a thread pool which handles all connections, instead of 1 thread = 1 connection like indy does by default. For IOCP, the only way to detect if a connection is still alive is to try writing to the socket. If there is any error, it means that the connection is closed. There are 2 options to detect disconnections:
1. If you use TsgcWebSocketClient, you can enable it in Options property, CleanDisconnect := True (by default is disabled). If it's enabled, before the client disconnects it sends a message informing the server about disconnection, so the server will receive this message and the OnDisconnect event will be raised.
2. You can enable heartbeat on the server side, for example every 60 seconds, so it will try to send a ping to all clients connected and if there is any client disconnected, OnDisconnect will be called.