ProstoServer is a universal library for building high-performance TCP servers running under Microsoft Windows. ProstoServer: manages client connections; sends and receives data asynchronously; organizes a pool of threads; provides basic protection against DoS attacks. The library is based on the Input/Output Completion Port (IOCP) mechanism - the most powerful tool for building servers in Windows operating systems. It allows ProstoServer to serve (for example, in the echo server mode) up to several thousand queries per second.