http://www.indyproject.org/docsite/html/WhatsNewIndy10.html
Indy10官方手册说支持IOCP:
Support for the Windows Fiber and IOCP APIs
Indy 10 provides experimental support for the Fiber and I/O Completion Ports API in the Windows platforms. This support is designed to aid in creating more scalable servers where thousands of simultaneous client connections are required. For small- and medium-sized projects, the traditional thread-based servers are still available.
Fiber and IOCP APIs are supported only for the Windows 2000, 2003, and XP operating systems using Delphi version 7. Windows 95, 98, and ME are not supported. Delphi compilers prior to version 7 are also unsupported due to critical changes in the VCL since those releases.